{"id":2456,"date":"2021-02-17T18:14:44","date_gmt":"2021-02-17T17:14:44","guid":{"rendered":"https:\/\/web.friendlycaptcha.com\/?p=2456"},"modified":"2026-05-06T09:46:53","modified_gmt":"2026-05-06T07:46:53","slug":"proof-of-work-captcha","status":"publish","type":"post","link":"https:\/\/friendlycaptcha.com\/it\/insights\/proof-of-work-captcha\/","title":{"rendered":"Prova di lavoro CAPTCHA: Controllo della varianza degli algoritmi"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"2456\" class=\"elementor elementor-2456\" data-elementor-post-type=\"post\">\n\t\t\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-2b0b9ba5 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"2b0b9ba5\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-58f9bbd3\" data-id=\"58f9bbd3\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-a11dd57 elementor-widget elementor-widget-heading\" data-id=\"a11dd57\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<div class=\"elementor-heading-title elementor-size-default\">Proof-of-Work CAPTCHA \u2013 At a Glance<\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<section class=\"elementor-section elementor-inner-section elementor-element elementor-element-55a13fc elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"55a13fc\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-50 elementor-inner-column elementor-element elementor-element-d281e82\" data-id=\"d281e82\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-5e45be1 elementor-position-inline-start elementor-view-default elementor-mobile-position-block-start elementor-widget elementor-widget-icon-box\" data-id=\"5e45be1\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"icon-box.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-icon-box-wrapper\">\n\n\t\t\t\t\t\t<div class=\"elementor-icon-box-icon\">\n\t\t\t\t<span  class=\"elementor-icon\">\n\t\t\t\t<svg aria-hidden=\"true\" class=\"e-font-icon-svg e-fas-cogs\" viewBox=\"0 0 640 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M512.1 191l-8.2 14.3c-3 5.3-9.4 7.5-15.1 5.4-11.8-4.4-22.6-10.7-32.1-18.6-4.6-3.8-5.8-10.5-2.8-15.7l8.2-14.3c-6.9-8-12.3-17.3-15.9-27.4h-16.5c-6 0-11.2-4.3-12.2-10.3-2-12-2.1-24.6 0-37.1 1-6 6.2-10.4 12.2-10.4h16.5c3.6-10.1 9-19.4 15.9-27.4l-8.2-14.3c-3-5.2-1.9-11.9 2.8-15.7 9.5-7.9 20.4-14.2 32.1-18.6 5.7-2.1 12.1.1 15.1 5.4l8.2 14.3c10.5-1.9 21.2-1.9 31.7 0L552 6.3c3-5.3 9.4-7.5 15.1-5.4 11.8 4.4 22.6 10.7 32.1 18.6 4.6 3.8 5.8 10.5 2.8 15.7l-8.2 14.3c6.9 8 12.3 17.3 15.9 27.4h16.5c6 0 11.2 4.3 12.2 10.3 2 12 2.1 24.6 0 37.1-1 6-6.2 10.4-12.2 10.4h-16.5c-3.6 10.1-9 19.4-15.9 27.4l8.2 14.3c3 5.2 1.9 11.9-2.8 15.7-9.5 7.9-20.4 14.2-32.1 18.6-5.7 2.1-12.1-.1-15.1-5.4l-8.2-14.3c-10.4 1.9-21.2 1.9-31.7 0zm-10.5-58.8c38.5 29.6 82.4-14.3 52.8-52.8-38.5-29.7-82.4 14.3-52.8 52.8zM386.3 286.1l33.7 16.8c10.1 5.8 14.5 18.1 10.5 29.1-8.9 24.2-26.4 46.4-42.6 65.8-7.4 8.9-20.2 11.1-30.3 5.3l-29.1-16.8c-16 13.7-34.6 24.6-54.9 31.7v33.6c0 11.6-8.3 21.6-19.7 23.6-24.6 4.2-50.4 4.4-75.9 0-11.5-2-20-11.9-20-23.6V418c-20.3-7.2-38.9-18-54.9-31.7L74 403c-10 5.8-22.9 3.6-30.3-5.3-16.2-19.4-33.3-41.6-42.2-65.7-4-10.9.4-23.2 10.5-29.1l33.3-16.8c-3.9-20.9-3.9-42.4 0-63.4L12 205.8c-10.1-5.8-14.6-18.1-10.5-29 8.9-24.2 26-46.4 42.2-65.8 7.4-8.9 20.2-11.1 30.3-5.3l29.1 16.8c16-13.7 34.6-24.6 54.9-31.7V57.1c0-11.5 8.2-21.5 19.6-23.5 24.6-4.2 50.5-4.4 76-.1 11.5 2 20 11.9 20 23.6v33.6c20.3 7.2 38.9 18 54.9 31.7l29.1-16.8c10-5.8 22.9-3.6 30.3 5.3 16.2 19.4 33.2 41.6 42.1 65.8 4 10.9.1 23.2-10 29.1l-33.7 16.8c3.9 21 3.9 42.5 0 63.5zm-117.6 21.1c59.2-77-28.7-164.9-105.7-105.7-59.2 77 28.7 164.9 105.7 105.7zm243.4 182.7l-8.2 14.3c-3 5.3-9.4 7.5-15.1 5.4-11.8-4.4-22.6-10.7-32.1-18.6-4.6-3.8-5.8-10.5-2.8-15.7l8.2-14.3c-6.9-8-12.3-17.3-15.9-27.4h-16.5c-6 0-11.2-4.3-12.2-10.3-2-12-2.1-24.6 0-37.1 1-6 6.2-10.4 12.2-10.4h16.5c3.6-10.1 9-19.4 15.9-27.4l-8.2-14.3c-3-5.2-1.9-11.9 2.8-15.7 9.5-7.9 20.4-14.2 32.1-18.6 5.7-2.1 12.1.1 15.1 5.4l8.2 14.3c10.5-1.9 21.2-1.9 31.7 0l8.2-14.3c3-5.3 9.4-7.5 15.1-5.4 11.8 4.4 22.6 10.7 32.1 18.6 4.6 3.8 5.8 10.5 2.8 15.7l-8.2 14.3c6.9 8 12.3 17.3 15.9 27.4h16.5c6 0 11.2 4.3 12.2 10.3 2 12 2.1 24.6 0 37.1-1 6-6.2 10.4-12.2 10.4h-16.5c-3.6 10.1-9 19.4-15.9 27.4l8.2 14.3c3 5.2 1.9 11.9-2.8 15.7-9.5 7.9-20.4 14.2-32.1 18.6-5.7 2.1-12.1-.1-15.1-5.4l-8.2-14.3c-10.4 1.9-21.2 1.9-31.7 0zM501.6 431c38.5 29.6 82.4-14.3 52.8-52.8-38.5-29.6-82.4 14.3-52.8 52.8z\"><\/path><\/svg>\t\t\t\t<\/span>\n\t\t\t<\/div>\n\t\t\t\n\t\t\t\t\t\t<div class=\"elementor-icon-box-content\">\n\n\t\t\t\t\t\t\t\t\t<p class=\"elementor-icon-box-title\">\n\t\t\t\t\t\t<span  >\n\t\t\t\t\t\t\tWhat is a proof-of-work CAPTCHA?\t\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/p>\n\t\t\t\t\n\t\t\t\t\t\t\t\t\t<p class=\"elementor-icon-box-description\">\n\t\t\t\t\t\tA proof-of-work CAPTCHA (PoW CAPTCHA) is designed to prevent automated abuse and spam by requiring a user's device to perform a computational task in the background.\t\t\t\t\t<\/p>\n\t\t\t\t\n\t\t\t<\/div>\n\t\t\t\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t<div class=\"elementor-column elementor-col-50 elementor-inner-column elementor-element elementor-element-b965d0e\" data-id=\"b965d0e\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-5f48342 elementor-position-inline-start elementor-view-default elementor-mobile-position-block-start elementor-widget elementor-widget-icon-box\" data-id=\"5f48342\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"icon-box.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-icon-box-wrapper\">\n\n\t\t\t\t\t\t<div class=\"elementor-icon-box-icon\">\n\t\t\t\t<span  class=\"elementor-icon\">\n\t\t\t\t<svg aria-hidden=\"true\" class=\"e-font-icon-svg e-fas-dice\" viewBox=\"0 0 640 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M592 192H473.26c12.69 29.59 7.12 65.2-17 89.32L320 417.58V464c0 26.51 21.49 48 48 48h224c26.51 0 48-21.49 48-48V240c0-26.51-21.49-48-48-48zM480 376c-13.25 0-24-10.75-24-24 0-13.26 10.75-24 24-24s24 10.74 24 24c0 13.25-10.75 24-24 24zm-46.37-186.7L258.7 14.37c-19.16-19.16-50.23-19.16-69.39 0L14.37 189.3c-19.16 19.16-19.16 50.23 0 69.39L189.3 433.63c19.16 19.16 50.23 19.16 69.39 0L433.63 258.7c19.16-19.17 19.16-50.24 0-69.4zM96 248c-13.25 0-24-10.75-24-24 0-13.26 10.75-24 24-24s24 10.74 24 24c0 13.25-10.75 24-24 24zm128 128c-13.25 0-24-10.75-24-24 0-13.26 10.75-24 24-24s24 10.74 24 24c0 13.25-10.75 24-24 24zm0-128c-13.25 0-24-10.75-24-24 0-13.26 10.75-24 24-24s24 10.74 24 24c0 13.25-10.75 24-24 24zm0-128c-13.25 0-24-10.75-24-24 0-13.26 10.75-24 24-24s24 10.74 24 24c0 13.25-10.75 24-24 24zm128 128c-13.25 0-24-10.75-24-24 0-13.26 10.75-24 24-24s24 10.74 24 24c0 13.25-10.75 24-24 24z\"><\/path><\/svg>\t\t\t\t<\/span>\n\t\t\t<\/div>\n\t\t\t\n\t\t\t\t\t\t<div class=\"elementor-icon-box-content\">\n\n\t\t\t\t\t\t\t\t\t<p class=\"elementor-icon-box-title\">\n\t\t\t\t\t\t<span  >\n\t\t\t\t\t\t\tLimits of typical proof-of-work challenges\t\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/p>\n\t\t\t\t\n\t\t\t\t\t\t\t\t\t<p class=\"elementor-icon-box-description\">\n\t\t\t\t\t\tSome devices solve the PoW challenge in seconds, others take ages \u2014 or give up. These unpredictable solving times create poor UX.\t\t\t\t\t<\/p>\n\t\t\t\t\n\t\t\t<\/div>\n\t\t\t\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"elementor-section elementor-inner-section elementor-element elementor-element-1f9b875 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"1f9b875\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-50 elementor-inner-column elementor-element elementor-element-ccfc096\" data-id=\"ccfc096\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-d9a01d8 elementor-position-inline-start elementor-view-default elementor-mobile-position-block-start elementor-widget elementor-widget-icon-box\" data-id=\"d9a01d8\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"icon-box.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-icon-box-wrapper\">\n\n\t\t\t\t\t\t<div class=\"elementor-icon-box-icon\">\n\t\t\t\t<span  class=\"elementor-icon\">\n\t\t\t\t<svg aria-hidden=\"true\" class=\"e-font-icon-svg e-fas-dice-d20\" viewBox=\"0 0 480 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M106.75 215.06L1.2 370.95c-3.08 5 .1 11.5 5.93 12.14l208.26 22.07-108.64-190.1zM7.41 315.43L82.7 193.08 6.06 147.1c-2.67-1.6-6.06.32-6.06 3.43v162.81c0 4.03 5.29 5.53 7.41 2.09zM18.25 423.6l194.4 87.66c5.3 2.45 11.35-1.43 11.35-7.26v-65.67l-203.55-22.3c-4.45-.5-6.23 5.59-2.2 7.57zm81.22-257.78L179.4 22.88c4.34-7.06-3.59-15.25-10.78-11.14L17.81 110.35c-2.47 1.62-2.39 5.26.13 6.78l81.53 48.69zM240 176h109.21L253.63 7.62C250.5 2.54 245.25 0 240 0s-10.5 2.54-13.63 7.62L130.79 176H240zm233.94-28.9l-76.64 45.99 75.29 122.35c2.11 3.44 7.41 1.94 7.41-2.1V150.53c0-3.11-3.39-5.03-6.06-3.43zm-93.41 18.72l81.53-48.7c2.53-1.52 2.6-5.16.13-6.78l-150.81-98.6c-7.19-4.11-15.12 4.08-10.78 11.14l79.93 142.94zm79.02 250.21L256 438.32v65.67c0 5.84 6.05 9.71 11.35 7.26l194.4-87.66c4.03-1.97 2.25-8.06-2.2-7.56zm-86.3-200.97l-108.63 190.1 208.26-22.07c5.83-.65 9.01-7.14 5.93-12.14L373.25 215.06zM240 208H139.57L240 383.75 340.43 208H240z\"><\/path><\/svg>\t\t\t\t<\/span>\n\t\t\t<\/div>\n\t\t\t\n\t\t\t\t\t\t<div class=\"elementor-icon-box-content\">\n\n\t\t\t\t\t\t\t\t\t<p class=\"elementor-icon-box-title\">\n\t\t\t\t\t\t<span  >\n\t\t\t\t\t\t\tHow Friendly Captcha revolutionized proof-of-work\t\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/p>\n\t\t\t\t\n\t\t\t\t\t\t\t\t\t<p class=\"elementor-icon-box-description\">\n\t\t\t\t\t\tInstead of giving the device one hard PoW challenge, Friendly Captcha asks it to solve multiple easier PoW challenges. This minimizes variance in solving times.\t\t\t\t\t<\/p>\n\t\t\t\t\n\t\t\t<\/div>\n\t\t\t\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t<div class=\"elementor-column elementor-col-50 elementor-inner-column elementor-element elementor-element-1c02b99\" data-id=\"1c02b99\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-057d0d5 elementor-position-inline-start elementor-view-default elementor-mobile-position-block-start elementor-widget elementor-widget-icon-box\" data-id=\"057d0d5\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"icon-box.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-icon-box-wrapper\">\n\n\t\t\t\t\t\t<div class=\"elementor-icon-box-icon\">\n\t\t\t\t<span  class=\"elementor-icon\">\n\t\t\t\t<svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xmlns:serif=\"http:\/\/www.serif.com\/\" width=\"100%\" height=\"100%\" viewBox=\"0 0 901 900\" xml:space=\"preserve\" style=\"fill-rule:evenodd;clip-rule:evenodd;stroke-linejoin:round;stroke-miterlimit:2;\"><g id=\"FriendlyCaptcha-AppIcon\"><rect x=\"0.4\" y=\"0\" width=\"900\" height=\"900\" style=\"fill:#fff;fill-opacity:0;\"><\/rect><g><path d=\"M708.045,216.655c-61.887,-61.887 -145.824,-96.655 -233.345,-96.655c-182.132,0 -330,147.868 -330,330c0,182.132 147.868,330 330,330c87.521,0 171.458,-34.768 233.345,-96.655l-70.003,-70.003c-43.321,43.321 -102.077,67.658 -163.342,67.658c-127.492,0 -231,-103.508 -231,-231c0,-127.492 103.508,-231 231,-231c61.265,0 120.021,24.337 163.342,67.658l70.003,-70.003Z\" style=\"fill:#ffab00;\"><\/path><path d=\"M241.355,683.345c61.887,61.887 145.824,96.655 233.345,96.655c87.521,0 171.458,-34.768 233.345,-96.655l-70.003,-70.003c-43.321,43.321 -102.077,67.658 -163.342,67.658c-61.265,0 -120.021,-24.337 -163.342,-67.658l-70.003,70.003Z\" style=\"fill:#ffc400;\"><\/path><circle cx=\"375.7\" cy=\"450\" r=\"49.5\" style=\"fill:#ffab00;\"><\/circle><circle cx=\"573.7\" cy=\"450\" r=\"49.5\" style=\"fill:#ffab00;\"><\/circle><\/g><\/g><\/svg>\t\t\t\t<\/span>\n\t\t\t<\/div>\n\t\t\t\n\t\t\t\t\t\t<div class=\"elementor-icon-box-content\">\n\n\t\t\t\t\t\t\t\t\t<p class=\"elementor-icon-box-title\">\n\t\t\t\t\t\t<span  >\n\t\t\t\t\t\t\tPioneer of next-gen, proof-of-work CAPTCHAs\t\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/p>\n\t\t\t\t\n\t\t\t\t\t\t\t\t\t<p class=\"elementor-icon-box-description\">\n\t\t\t\t\t\tFriendly Captcha reinvented proof-of-work for CAPTCHAs. It offers better UX, lower abandonment, and better reliability. <b><a href=\"https:\/\/friendlycaptcha.com\/signup\/\">Try out now \u203a <\/a><\/b> \n\t\t\t\t\t<\/p>\n\t\t\t\t\n\t\t\t<\/div>\n\t\t\t\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<div class=\"elementor-element elementor-element-890c2cc elementor-widget elementor-widget-spacer\" data-id=\"890c2cc\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-a996c89 elementor-widget elementor-widget-heading\" data-id=\"a996c89\" data-element_type=\"widget\" data-e-type=\"widget\" data-no-translation=\"\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<style>.elementor-element-a996c89{display:none !important}<\/style>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-676daa0 elementor-widget elementor-widget-spacer\" data-id=\"676daa0\" data-element_type=\"widget\" data-e-type=\"widget\" data-no-translation=\"\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<style>.elementor-element-676daa0{display:none !important}<\/style>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-37e97c1 elementor-widget elementor-widget-heading\" data-id=\"37e97c1\" data-element_type=\"widget\" data-e-type=\"widget\" data-no-translation=\"\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<style>.elementor-element-37e97c1{display:none !important}<\/style>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-7d98bb8 elementor-widget elementor-widget-spacer\" data-id=\"7d98bb8\" data-element_type=\"widget\" data-e-type=\"widget\" data-no-translation=\"\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<style>.elementor-element-7d98bb8{display:none !important}<\/style>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-65674ea7 elementor-widget elementor-widget-text-editor\" data-id=\"65674ea7\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>A Proof-of-Work CAPTCHA (PoW CAPTCHA) is a bot-prevention tool that asks the user\u2019s device to solve a small computational puzzle in the background. Instead of making people click on traffic lights or decipher distorted text, the browser does the work automatically.<\/p>\n<p>The result is often a smoother experience: no visual challenge, no unnecessary tracking, and usually only a short wait of a few seconds. For bots, however, the cost adds up. Every request requires device time and energy, which makes large-scale abuse more expensive.<\/p>\n<p>But standard proof-of-work algorithms have a problem: they don&#8217;t measure progress. Solving the puzzle is like playing a lottery over and over until you win. Losing many times does not make the next attempt more likely to succeed.<\/p>\n<p>That randomness creates a critical challenge for CAPTCHAs. If proof-of-work isn&#8217;t used properly, the CAPTCHA challenge turns into a lottery. One user might win on the first attempt, completing it in one second, while another legitimate user may need many attempts, waiting ten seconds. For websites and web applications that need to stop bots without frustrating real people, that kind of variance is unacceptable.<\/p>\n<p>That is why we built Friendly Captcha, a user-friendly, <span style=\"font-family: var( --e-global-typography-2d35f3d-font-family ), Sans-serif; font-size: var( --e-global-typography-2d35f3d-font-size );\"><a href=\"https:\/\/friendlycaptcha.com\/insights\/open-source-captcha\/\">open source captcha<\/a><\/span>\u00a0based on proof of work. Friendly Captcha solves the variance issue with a more sophisticated proof-of-work system: instead of relying on one hard, lottery-style puzzle, it splits the work into multiple smaller cryptographic puzzles. This makes solve times more predictable, smooths out unlucky outliers, and allows the widget to show progress instead of leaving users waiting blindly.<\/p>\n<p>Friendly Captcha\u2019s proof-of-work challenge doesn\u2019t just make attacks expensive. It also makes solve times predictable and fair. We believe a good CAPTCHA should require roughly the same amount of computation from comparable devices, without ever blocking real humans.<\/p>\n<p><!-- \/wp:paragraph --><!-- wp:paragraph --><\/p>\n<h2>Our proof-of-work setup<\/h2>\n<p><!-- \/wp:heading --><!-- wp:paragraph --><\/p>\n<p>The idea behind PoW is that the puzzle (also called a <em>challenge<\/em>) must be cheap to verify, but expensive to compute.<\/p>\n<p><!-- \/wp:paragraph --><!-- wp:paragraph --><\/p>\n<p>A PoW that would be \u201chash this string 1 million times\u201d would be expensive to compute, but just as expensive to verify. Instead most PoW algorithms make the user search for a needle in a haystack: we generate a <em>puzzle string<\/em> <code>p<\/code>, and ask the user to find a <em>nonce<\/em> <code>q<\/code> such that the hash of <code>p<\/code> and <code>q<\/code> concatenated meets some rare criteria. If we use a good hash function, any input string is just as likely to meet this criteria as another.<\/p>\n<p><!-- \/wp:paragraph --><!-- wp:paragraph --><\/p>\n<p>Remember that any bytes or string can be interpreted as a number. We take the first 4 bytes of the hash and interpret them as a 32 bit integer. If that number is below some threshold T (which you could call the inverse of the difficulty) then it is a valid solution. Any hash input is equally likely to meet that criteria, so to find the solution the user would just try different values for the nonce <code>q<\/code> until they find a winning solution. Not so different from playing the lottery a lot!<\/p>\n<p><!-- \/wp:paragraph --><!-- wp:paragraph --><\/p>\n<p><strong>Verification in pseudocode<\/strong><\/p>\n<p><!-- \/wp:paragraph --><!-- wp:code --><\/p>\n<pre><code>puzzleString = \"my-puzzle-string\"\nthreshold = 1000 \/\/ The lower the more difficult the puzzle is\nnonce = \"3456356782345\" \/\/ This is the value the solver changes to try and find a valid solution\n\nhash_result = hash(puzzleString + nonce)\nvalue = toUint32(hash_result[0:4])\n\nif value &lt; threshold {\n    print \"Valid!\"\n} else {\n    print \"Invalid solution :(\"\n}<\/code><\/pre>\n<p><!-- \/wp:code --><!-- wp:heading {\"level\":3} --><\/p>\n<h2>How many tries does it take?<\/h2>\n<p><!-- \/wp:heading --><!-- wp:paragraph --><\/p>\n<p>If your chances of winning the lotery are one in a million, after a million tries your odds of winning at least once is around 63.2% (<code>1 - (1\/one_million)^one_million<\/code> or <code>1 - binom.pmf(1, one_million, 1\/one_million)<\/code>). Here\u2019s a density plot:<\/p>\n<p><!-- \/wp:paragraph --><!-- wp:image {\"id\":2457,\"sizeSlug\":\"large\",\"linkDestination\":\"none\"} --><\/p>\n<figure><img decoding=\"async\" src=\"https:\/\/friendlycaptcha.com\/wp-content\/uploads\/2021\/02\/l5KjMXu.png\" alt=\"\" \/><\/figure>\n<p><!-- \/wp:image --><!-- wp:paragraph --><\/p>\n<p>Most people take around a million attempts, but some users will be really unlucky and instead need 3 million attemps (~5% in fact) or even more! In other words: there is a large amount of variance in how many attempts are needed. This is problematic for a PoW CAPTCHA: the user will give up on waiting if it takes 5 times longer than expected. They don\u2019t care what the mathematical average is, they just want to sign up to your website.<\/p>\n<p><!-- \/wp:paragraph --><!-- wp:paragraph --><\/p>\n<p>For a decent user experience the user also deserves some sort of progress indicator. Just showing <em>\u201csolving the captcha\u201d<\/em> for 10 seconds without any indication of will make the user give up and think the website is broken. If instead there is a progress bar that increases over time it\u2019s much more tolerable.<\/p>\n<p><!-- \/wp:paragraph --><!-- wp:paragraph --><\/p>\n<p>The issue is that there is no progress, nobody knows when they will find the nonce that creates a hash that satisfies the criteria. Fortunately, there is a straightforward solution to both the progress and variance issue: we ask users to find more than one nonce.<\/p>\n<p><!-- \/wp:paragraph --><!-- wp:heading {\"level\":3} --><\/p>\n<h2>Multiple, easier problems<\/h2>\n<p><!-- \/wp:heading --><!-- wp:paragraph --><\/p>\n<p>Instead of making the user find the 1 in a million nonce, we can make them find 10 nonces to a 1 in 100k problem. The expected number of attempts is still the same, but now we can show a progress bar to the user!<\/p>\n<p><!-- \/wp:paragraph --><!-- wp:paragraph --><\/p>\n<p>Not only do we solve the progress problem, we also decrease the variance of how many attempts were required in total. As we increase the number of nonces we ask, the variance decreases. Let\u2019s plot that:<\/p>\n<p><!-- \/wp:paragraph --><!-- wp:code --><\/p>\n<pre><code>import matplotlib.pyplot as plt\nimport numpy as np\nfrom scipy.stats import binom\n\none_million = 1000000\n\nn_attempts = np.arange(0, 5*one_million, 1000)\n\nfraction_still_solving_1m = [binom.cdf(1, n, 1\/one_million) for n in n_attempts]\nfraction_still_solving_500k = [binom.cdf(2, n, 2\/one_million) for n in n_attempts]\nfraction_still_solving_200k = [binom.cdf(5, n, 5\/one_million) for n in n_attempts]\nfraction_still_solving_100k = [binom.cdf(10, n, 10\/one_million) for n in n_attempts]\nfraction_still_solving_50k = [binom.cdf(20, n, 20\/one_million) for n in n_attempts]\n\nplt.figure(figsize=(12, 6))\nplt.plot(n_attempts, fraction_still_solving_1m, label=\"1 lottery win, 1\/1M\")\nplt.plot(n_attempts, fraction_still_solving_500k, label=\"2 lottery wins, 1\/500K\")\nplt.plot(n_attempts, fraction_still_solving_200k, label=\"5 lottery wins, 1\/200K\")\nplt.plot(n_attempts, fraction_still_solving_100k, label=\"10 lottery wins, 1\/100K\")\nplt.plot(n_attempts, fraction_still_solving_50k, label=\"20 lottery wins, 1\/50K\")\nplt.legend()\nplt.ylabel(\"Fraction who aren't done yet\")\nplt.xlabel(\"Amount of attempts\")\nplt.show()<\/code><\/pre>\n<p><!-- \/wp:code --><!-- wp:image {\"id\":2458,\"sizeSlug\":\"large\",\"linkDestination\":\"none\"} --><\/p>\n<figure><img decoding=\"async\" src=\"https:\/\/friendlycaptcha.com\/wp-content\/uploads\/2021\/02\/AJxyk8n.png\" alt=\"\" \/><\/figure>\n<p><!-- \/wp:image --><!-- wp:paragraph --><\/p>\n<p>Looking at this plot we can see that if we have people play a single lottery around 1 in 10 people will take more than 4 times longer than average! That\u2019s unacceptable for a CAPTCHA, but as we increase the amount of wins required for a simpler lottery we decrease the variance considerably. In table form, how many people would not be done yet after N attempts:<\/p>\n<p><!-- \/wp:paragraph --><!-- wp:table --><\/p>\n<figure>\n<table>\n<thead>\n<tr>\n<th>Amount of solutions required<\/th>\n<th>1M attempts<\/th>\n<th>2M attempts<\/th>\n<th>3M attempts<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>1<\/td>\n<td>one in 1.4<\/td>\n<td>one in 2.5<\/td>\n<td>one in 2.5<\/td>\n<\/tr>\n<tr>\n<td>2<\/td>\n<td>one in 1.5<\/td>\n<td>one in 4.2<\/td>\n<td>one in 16<\/td>\n<\/tr>\n<tr>\n<td>5<\/td>\n<td>one in 1.6<\/td>\n<td>one in 14.9<\/td>\n<td>one in 358<\/td>\n<\/tr>\n<tr>\n<td>10<\/td>\n<td>one in 1.7<\/td>\n<td>one in 92.5<\/td>\n<td>one in 45K<\/td>\n<\/tr>\n<tr>\n<td>20<\/td>\n<td>one in 1.8<\/td>\n<td>one in 2715<\/td>\n<td>one in 512M<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p><!-- \/wp:table --><!-- wp:paragraph --><\/p>\n<p>We can also plot the probability mass function (below) which shows the variance clearly as well, the expected number of attempts is about the same, but the variance is much lower.<\/p>\n<p><!-- \/wp:paragraph --><!-- wp:image --><\/p>\n<figure><img decoding=\"async\" src=\"https:\/\/i.imgur.com\/UNEq0Mq.png\" alt=\"https:\/\/i.imgur.com\/UNEq0Mq.png\" \/><\/figure>\n<p><!-- \/wp:image --><!-- wp:heading {\"level\":3} --><\/p>\n<h2>The downsides of requiring more solutions<\/h2>\n<p><!-- \/wp:heading --><!-- wp:paragraph --><\/p>\n<p>There are some downsides to requiring more solutions, the first is the need to submit more solutions requiring a bit more bandwidth. In Friendly Captcha every solution is an 8 byte value transmitted as base64, so going from 10 to 20 solutions would take around 106 extra characters (<code>10*8*(4\/3)<\/code>).<\/p>\n<p><!-- \/wp:paragraph --><!-- wp:paragraph --><\/p>\n<p>Secondly there are simply more solutions to verify, but given that verification is cheap this doesn\u2019t matter.<\/p>\n<p><!-- \/wp:paragraph --><!-- wp:heading {\"level\":3} --><\/p>\n<h2>Conclusion<\/h2>\n<p><!-- \/wp:heading --><!-- wp:paragraph --><\/p>\n<p>Proof of work usually doesn\u2019t have any notion of progress. Any attempt is just as likely as the next to find the solution. By requiring multiple proof of work solutions we can decrease variance, as well as provide a notion of progress, both of these features are requirements for a CAPTCHA based on proof of work.<\/p>\n<p><!-- \/wp:paragraph --><!-- wp:paragraph --><\/p>\n<p>Want to see the proof of work CAPTCHA in action? Try the demo <a href=\"https:\/\/friendlycaptcha.com\/#demo\" data-type=\"URL\" data-id=\"https:\/\/friendlycaptcha.com\/#demo\">here<\/a>. The open source CAPTCHA library and the widget code is found <a href=\"https:\/\/github.com\/friendlycaptcha\/friendly-challenge\" target=\"_blank\" rel=\"noreferrer noopener\">here<\/a>.<\/p>\n<p>\u00a0<\/p>\n<h3>FAQ<\/h3>\n<p><!-- \/wp:paragraph --><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-dfb1dd4 elementor-widget elementor-widget-accordion\" data-id=\"dfb1dd4\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"accordion.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-accordion\">\n\t\t\t\t\t\t\t<div class=\"elementor-accordion-item\">\n\t\t\t\t\t<div id=\"elementor-tab-title-2341\" class=\"elementor-tab-title\" data-tab=\"1\" role=\"button\" aria-controls=\"elementor-tab-content-2341\" aria-expanded=\"false\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon elementor-accordion-icon-left\" aria-hidden=\"true\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon-closed\"><svg class=\"e-font-icon-svg e-fas-plus\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M416 208H272V64c0-17.67-14.33-32-32-32h-32c-17.67 0-32 14.33-32 32v144H32c-17.67 0-32 14.33-32 32v32c0 17.67 14.33 32 32 32h144v144c0 17.67 14.33 32 32 32h32c17.67 0 32-14.33 32-32V304h144c17.67 0 32-14.33 32-32v-32c0-17.67-14.33-32-32-32z\"><\/path><\/svg><\/span>\n\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon-opened\"><svg class=\"e-font-icon-svg e-fas-minus\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M416 208H32c-17.67 0-32 14.33-32 32v32c0 17.67 14.33 32 32 32h384c17.67 0 32-14.33 32-32v-32c0-17.67-14.33-32-32-32z\"><\/path><\/svg><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"elementor-accordion-title\" tabindex=\"0\">What is a Proof-of-Work CAPTCHA?<\/a>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<div id=\"elementor-tab-content-2341\" class=\"elementor-tab-content elementor-clearfix\" data-tab=\"1\" role=\"region\" aria-labelledby=\"elementor-tab-title-2341\"><p data-pm-slice=\"1 1 []\">A Proof-of-Work (PoW) CAPTCHA like Friendly Captcha is the modern, user-friendly security mechanism. It prevents bot abuse by requiring a user&#8217;s browser to perform a small, hidden computational task rather than solving visual puzzles. Friendly Captcha&#8217;s PoW approach shifts the cost of bot protection from human effort to computational resources, making large-scale bot attacks too expensive.<\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<div class=\"elementor-accordion-item\">\n\t\t\t\t\t<div id=\"elementor-tab-title-2342\" class=\"elementor-tab-title\" data-tab=\"2\" role=\"button\" aria-controls=\"elementor-tab-content-2342\" aria-expanded=\"false\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon elementor-accordion-icon-left\" aria-hidden=\"true\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon-closed\"><svg class=\"e-font-icon-svg e-fas-plus\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M416 208H272V64c0-17.67-14.33-32-32-32h-32c-17.67 0-32 14.33-32 32v144H32c-17.67 0-32 14.33-32 32v32c0 17.67 14.33 32 32 32h144v144c0 17.67 14.33 32 32 32h32c17.67 0 32-14.33 32-32V304h144c17.67 0 32-14.33 32-32v-32c0-17.67-14.33-32-32-32z\"><\/path><\/svg><\/span>\n\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon-opened\"><svg class=\"e-font-icon-svg e-fas-minus\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M416 208H32c-17.67 0-32 14.33-32 32v32c0 17.67 14.33 32 32 32h384c17.67 0 32-14.33 32-32v-32c0-17.67-14.33-32-32-32z\"><\/path><\/svg><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"elementor-accordion-title\" tabindex=\"0\">How does proof-of-work CAPTCHA improve security?<\/a>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<div id=\"elementor-tab-content-2342\" class=\"elementor-tab-content elementor-clearfix\" data-tab=\"2\" role=\"region\" aria-labelledby=\"elementor-tab-title-2342\"><p>Proof-of-work CAPTCHA increases bot protection by requiring a small cryptographic puzzle to be solved using computational resources. While humans aren&#8217;t affected, this mechanism slows down bots and makes large-scale automated attacks impractical.<\/p>\n<p>The best proof-of-work CAPTCHA is Friendly Captcha. For maximum security, it combines proof-of-work mechanisms with advanced risk scaling to eliminate bot attacks and advanced spam protection.<\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<div class=\"elementor-accordion-item\">\n\t\t\t\t\t<div id=\"elementor-tab-title-2343\" class=\"elementor-tab-title\" data-tab=\"3\" role=\"button\" aria-controls=\"elementor-tab-content-2343\" aria-expanded=\"false\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon elementor-accordion-icon-left\" aria-hidden=\"true\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon-closed\"><svg class=\"e-font-icon-svg e-fas-plus\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M416 208H272V64c0-17.67-14.33-32-32-32h-32c-17.67 0-32 14.33-32 32v144H32c-17.67 0-32 14.33-32 32v32c0 17.67 14.33 32 32 32h144v144c0 17.67 14.33 32 32 32h32c17.67 0 32-14.33 32-32V304h144c17.67 0 32-14.33 32-32v-32c0-17.67-14.33-32-32-32z\"><\/path><\/svg><\/span>\n\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon-opened\"><svg class=\"e-font-icon-svg e-fas-minus\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M416 208H32c-17.67 0-32 14.33-32 32v32c0 17.67 14.33 32 32 32h384c17.67 0 32-14.33 32-32v-32c0-17.67-14.33-32-32-32z\"><\/path><\/svg><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"elementor-accordion-title\" tabindex=\"0\">How does Friendly Captcha work?<\/a>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<div id=\"elementor-tab-content-2343\" class=\"elementor-tab-content elementor-clearfix\" data-tab=\"3\" role=\"region\" aria-labelledby=\"elementor-tab-title-2343\"><p data-pm-slice=\"1 1 []\">Friendly Captcha is a privacy-first, proof-of-work-based bot protection system. It works by having the user&#8217;s browser solve a complex cryptographic puzzle in the background while the user fills out a form. This eliminates the need to click traffic lights or decipher text. Friendly Captcha is GDPR-compliant, uses no cookies, and provides users with a frictionless experience.<\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<div class=\"elementor-accordion-item\">\n\t\t\t\t\t<div id=\"elementor-tab-title-2344\" class=\"elementor-tab-title\" data-tab=\"4\" role=\"button\" aria-controls=\"elementor-tab-content-2344\" aria-expanded=\"false\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon elementor-accordion-icon-left\" aria-hidden=\"true\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon-closed\"><svg class=\"e-font-icon-svg e-fas-plus\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M416 208H272V64c0-17.67-14.33-32-32-32h-32c-17.67 0-32 14.33-32 32v144H32c-17.67 0-32 14.33-32 32v32c0 17.67 14.33 32 32 32h144v144c0 17.67 14.33 32 32 32h32c17.67 0 32-14.33 32-32V304h144c17.67 0 32-14.33 32-32v-32c0-17.67-14.33-32-32-32z\"><\/path><\/svg><\/span>\n\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon-opened\"><svg class=\"e-font-icon-svg e-fas-minus\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M416 208H32c-17.67 0-32 14.33-32 32v32c0 17.67 14.33 32 32 32h384c17.67 0 32-14.33 32-32v-32c0-17.67-14.33-32-32-32z\"><\/path><\/svg><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"elementor-accordion-title\" tabindex=\"0\">What is the best Proof-of-Work CAPTCHA?<\/a>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<div id=\"elementor-tab-content-2344\" class=\"elementor-tab-content elementor-clearfix\" data-tab=\"4\" role=\"region\" aria-labelledby=\"elementor-tab-title-2344\"><p data-pm-slice=\"1 1 []\"><a class=\"H23r4e\" href=\"https:\/\/friendlycaptcha.com\/\"><strong>Friendly Captcha<\/strong><\/a> is widely considered the best Proof-of-Work (PoW) CAPTCHA in 2026 for modern web and web applications. It offers a privacy-first, GDPR-compliant CAPTCHA solution that operates invisibly in the background. It improves upon traditional PoW methods by using multiple, lighter, and adjustable cryptographic puzzles to ensure excellent user experience and accessibility (WCAG 2.2. Level AA).<\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<div class=\"elementor-accordion-item\">\n\t\t\t\t\t<div id=\"elementor-tab-title-2345\" class=\"elementor-tab-title\" data-tab=\"5\" role=\"button\" aria-controls=\"elementor-tab-content-2345\" aria-expanded=\"false\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon elementor-accordion-icon-left\" aria-hidden=\"true\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon-closed\"><svg class=\"e-font-icon-svg e-fas-plus\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M416 208H272V64c0-17.67-14.33-32-32-32h-32c-17.67 0-32 14.33-32 32v144H32c-17.67 0-32 14.33-32 32v32c0 17.67 14.33 32 32 32h144v144c0 17.67 14.33 32 32 32h32c17.67 0 32-14.33 32-32V304h144c17.67 0 32-14.33 32-32v-32c0-17.67-14.33-32-32-32z\"><\/path><\/svg><\/span>\n\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon-opened\"><svg class=\"e-font-icon-svg e-fas-minus\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M416 208H32c-17.67 0-32 14.33-32 32v32c0 17.67 14.33 32 32 32h384c17.67 0 32-14.33 32-32v-32c0-17.67-14.33-32-32-32z\"><\/path><\/svg><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"elementor-accordion-title\" tabindex=\"0\">How is Proof-of-Work verified?<\/a>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<div id=\"elementor-tab-content-2345\" class=\"elementor-tab-content elementor-clearfix\" data-tab=\"5\" role=\"region\" aria-labelledby=\"elementor-tab-title-2345\"><p data-pm-slice=\"1 1 []\">In Proof-of-Work (PoW), network nodes verify a miner&#8217;s submitted block hash by checking that it is lower than the target threshold. This ensures that the &#8220;work&#8221; (computational effort) was actually performed. This verification process is inexpensive, enabling nodes to swiftly validate transactions without repeating the energy-intensive search for the solution.<\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<div class=\"elementor-accordion-item\">\n\t\t\t\t\t<div id=\"elementor-tab-title-2346\" class=\"elementor-tab-title\" data-tab=\"6\" role=\"button\" aria-controls=\"elementor-tab-content-2346\" aria-expanded=\"false\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon elementor-accordion-icon-left\" aria-hidden=\"true\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon-closed\"><svg class=\"e-font-icon-svg e-fas-plus\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M416 208H272V64c0-17.67-14.33-32-32-32h-32c-17.67 0-32 14.33-32 32v144H32c-17.67 0-32 14.33-32 32v32c0 17.67 14.33 32 32 32h144v144c0 17.67 14.33 32 32 32h32c17.67 0 32-14.33 32-32V304h144c17.67 0 32-14.33 32-32v-32c0-17.67-14.33-32-32-32z\"><\/path><\/svg><\/span>\n\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon-opened\"><svg class=\"e-font-icon-svg e-fas-minus\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M416 208H32c-17.67 0-32 14.33-32 32v32c0 17.67 14.33 32 32 32h384c17.67 0 32-14.33 32-32v-32c0-17.67-14.33-32-32-32z\"><\/path><\/svg><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"elementor-accordion-title\" tabindex=\"0\">How does Proof-of-Work CAPTCHAs compare to traditional CAPTCHAs?<\/a>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<div id=\"elementor-tab-content-2346\" class=\"elementor-tab-content elementor-clearfix\" data-tab=\"6\" role=\"region\" aria-labelledby=\"elementor-tab-title-2346\"><p data-pm-slice=\"1 1 []\">Proof-of-Work CAPTCHAs, such as Friendly Captcha, differ from traditional CAPTCHAs, like <a href=\"https:\/\/friendlycaptcha.com\/insights\/hcaptcha-vs-recaptcha\/\">reCAPTCHA or hCaptcha<\/a>, in that they require a device to solve a small, invisible cryptographic puzzle, rather than asking humans to identify images or text. Friendly Captcha prioritizes user experience, <a href=\"https:\/\/friendlycaptcha.com\/privacy\/\">privacy<\/a>, and <a href=\"https:\/\/friendlycaptcha.com\/accessibility\/\">accessibility<\/a>, offering an invisible, barrier-free, and privacy-compliant alternative to traditional CAPTCHA verification methods.<\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<div class=\"elementor-accordion-item\">\n\t\t\t\t\t<div id=\"elementor-tab-title-2347\" class=\"elementor-tab-title\" data-tab=\"7\" role=\"button\" aria-controls=\"elementor-tab-content-2347\" aria-expanded=\"false\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon elementor-accordion-icon-left\" aria-hidden=\"true\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon-closed\"><svg class=\"e-font-icon-svg e-fas-plus\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M416 208H272V64c0-17.67-14.33-32-32-32h-32c-17.67 0-32 14.33-32 32v144H32c-17.67 0-32 14.33-32 32v32c0 17.67 14.33 32 32 32h144v144c0 17.67 14.33 32 32 32h32c17.67 0 32-14.33 32-32V304h144c17.67 0 32-14.33 32-32v-32c0-17.67-14.33-32-32-32z\"><\/path><\/svg><\/span>\n\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon-opened\"><svg class=\"e-font-icon-svg e-fas-minus\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M416 208H32c-17.67 0-32 14.33-32 32v32c0 17.67 14.33 32 32 32h384c17.67 0 32-14.33 32-32v-32c0-17.67-14.33-32-32-32z\"><\/path><\/svg><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"elementor-accordion-title\" tabindex=\"0\">Is a PoW CAPTCHA GDPR compliant?<\/a>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<div id=\"elementor-tab-content-2347\" class=\"elementor-tab-content elementor-clearfix\" data-tab=\"7\" role=\"region\" aria-labelledby=\"elementor-tab-title-2347\"><p data-pm-slice=\"1 1 []\">Yes, Proof-of-Work CAPTCHAs are generally considered GDPR-compliant and privacy-first because they function without collecting, storing, or tracking personal data. They avoid processing personal user information by using cryptographic puzzles that are solved by the user&#8217;s browser in the background. This makes them a privacy-focused <a href=\"https:\/\/friendlycaptcha.com\/insights\/captcha-alternative\/\">CAPTCHA alternative<\/a> to traditional, tracking-heavy CAPTCHAs, such as reCAPTCHA or hCaptcha.<\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<div class=\"elementor-accordion-item\">\n\t\t\t\t\t<div id=\"elementor-tab-title-2348\" class=\"elementor-tab-title\" data-tab=\"8\" role=\"button\" aria-controls=\"elementor-tab-content-2348\" aria-expanded=\"false\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon elementor-accordion-icon-left\" aria-hidden=\"true\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon-closed\"><svg class=\"e-font-icon-svg e-fas-plus\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M416 208H272V64c0-17.67-14.33-32-32-32h-32c-17.67 0-32 14.33-32 32v144H32c-17.67 0-32 14.33-32 32v32c0 17.67 14.33 32 32 32h144v144c0 17.67 14.33 32 32 32h32c17.67 0 32-14.33 32-32V304h144c17.67 0 32-14.33 32-32v-32c0-17.67-14.33-32-32-32z\"><\/path><\/svg><\/span>\n\t\t\t\t\t\t\t\t<span class=\"elementor-accordion-icon-opened\"><svg class=\"e-font-icon-svg e-fas-minus\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M416 208H32c-17.67 0-32 14.33-32 32v32c0 17.67 14.33 32 32 32h384c17.67 0 32-14.33 32-32v-32c0-17.67-14.33-32-32-32z\"><\/path><\/svg><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"elementor-accordion-title\" tabindex=\"0\">Can bots solve PoW CAPTCHAs?<\/a>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<div id=\"elementor-tab-content-2348\" class=\"elementor-tab-content elementor-clearfix\" data-tab=\"8\" role=\"region\" aria-labelledby=\"elementor-tab-title-2348\"><p data-pm-slice=\"1 1 []\">Yes, bots can solve CAPTCHAs using the proof-of-work system. However, the goal of these systems is to make automated solving computationally expensive and slow, rather than impossible. Friendly Captcha detects high-volume spam and sophisticated attackers by combining PoW&#8217;s economic barrier with its international risk database. It analyzes patterns across millions of daily requests without tracking individual users or collecting personal data.<\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-dad43d9 elementor-widget elementor-widget-text-editor\" data-id=\"dad43d9\" data-element_type=\"widget\" data-e-type=\"widget\" data-no-translation=\"\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<style>.elementor-element-dad43d9{display:none !important}<\/style>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-a8f53c6 elementor-widget elementor-widget-accordion\" data-id=\"a8f53c6\" data-element_type=\"widget\" data-e-type=\"widget\" data-no-translation=\"\" data-widget_type=\"accordion.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<style>.elementor-element-a8f53c6{display:none !important}<\/style>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-378f6f1 elementor-widget elementor-widget-text-editor\" data-id=\"378f6f1\" data-element_type=\"widget\" data-e-type=\"widget\" data-no-translation=\"\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<style>.elementor-element-378f6f1{display:none !important}<\/style>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-5d6bc74 elementor-widget elementor-widget-accordion\" data-id=\"5d6bc74\" data-element_type=\"widget\" data-e-type=\"widget\" data-no-translation=\"\" data-widget_type=\"accordion.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<style>.elementor-element-5d6bc74{display:none !important}<\/style>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>Proof-of-Work CAPTCHA \u2013 At a Glance What is a proof-of-work CAPTCHA? A proof-of-work CAPTCHA (PoW CAPTCHA) is designed to prevent automated abuse and spam by requiring a user&#8217;s device to perform a computational task in the background. Limits of typical proof-of-work challenges Some devices solve the PoW challenge in seconds, others take ages \u2014 or [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":10158,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[24],"tags":[37],"class_list":["post-2456","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-insights","tag-captcha-alternatives"],"_links":{"self":[{"href":"https:\/\/friendlycaptcha.com\/it\/wp-json\/wp\/v2\/posts\/2456","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/friendlycaptcha.com\/it\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/friendlycaptcha.com\/it\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/friendlycaptcha.com\/it\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/friendlycaptcha.com\/it\/wp-json\/wp\/v2\/comments?post=2456"}],"version-history":[{"count":0,"href":"https:\/\/friendlycaptcha.com\/it\/wp-json\/wp\/v2\/posts\/2456\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/friendlycaptcha.com\/it\/wp-json\/wp\/v2\/media\/10158"}],"wp:attachment":[{"href":"https:\/\/friendlycaptcha.com\/it\/wp-json\/wp\/v2\/media?parent=2456"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/friendlycaptcha.com\/it\/wp-json\/wp\/v2\/categories?post=2456"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/friendlycaptcha.com\/it\/wp-json\/wp\/v2\/tags?post=2456"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}