
reCAPTCHA
hCaptcha
Cloudflare Turnstile
Akismet
Private Captcha
mosparo
Cap Captcha
ALTCHA is a free CAPTCHA alternative that uses a proof-of-work mechanism to protect your website, and online services from spam.

hCaptcha
reCAPTCHA
Cloudflare Turnstile
Akismet
AuthKong
Protect your website forms from spam and fake signups without annoying captchas. Privacy-first security with zero fingerprinting. Try it now.

Which is more popular?
Based on our record, ALTCHA seems to be more popular. It has been mentioned 3 times since March 2021.
Website, pricing, platforms and company facts side by side.
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| Website | altcha.org | sharkeyes.dev |
| Pricing | ||
| Platforms | — | |
| Company | — | Startup from Israel · 1 - 9 employees · 2025 |
| Listed in |
In their own words, as submitted to SaaSHub.


ALTCHA uses a proof-of-work mechanism to protect your website, APIs, and online services from spam and unwanted content. Unlike other solutions, ALTCHA is free, open-source and self-hosted, without external services, does not use cookies nor fingerprinting, does not track users, and is fully...
Tired of spam bots attacking your website forms? Fake registrations, junk inquiries, and comment spam standard CAPTCHAs dont help. They only frustrate real users while "smart" bots bypass them anyway. SharkEyes takes a different approach. The system quietly detects spam and fake registrations in...
What each product offers, as listed by its team.


How often each product is chosen within a category, 0–100% relative to the other.


As answered by people managing ALTCHA and SharkEyes.dev.
ALTCHA's answer
What makes ALTCHA unique is that it is free, open-source and self-hosted, without external services, does not use cookies nor fingerprinting, does not track users, and is fully compliant with GDPR. Unlike other captcha solutions, ALTCHA does not require users to solve puzzles or captchas and uses a proof-of-work mechanism instead.
SharkEyes.dev's answer:
SharkEyes delivers privacy first spam and bot protection without annoying captchas or invasive browser fingerprinting. It blocks automated submissions seamlessly in the background, ensuring a frictionless user experience while fully
ALTCHA's answer
Here are some key reasons why a person should choose ALTCHA over its competitors:
So in summary, ALTCHA's privacy compliance, open design, accessibility, machine compatibility and modern approach give it clear advantages over competing captcha solutions.
SharkEyes.dev's answer:
Traditional captchas ruin user experience and lower conversion rates, while big security vendors often track user data across the web. SharkEyes balances high-grade security with complete user privacy and zero user friction, making it quick to deploy, affordable for growing businesses.
ALTCHA's answer
JavaScript and Svelte.
SharkEyes.dev's answer:
JavaScript, Golang, Python, REST API, Webhooks, Cloud Infrastructure, Bash, and Lightweight Anomaly Detection Algorithms.
ALTCHA's answer
Our primary audience for ALTCHA Forms includes enterprises, medium and small businesses, non-profits, and individuals who need a reliable, secure, and compliant solution for data collection and management. Whether you're a large corporation dealing with extensive regulatory requirements, a small business looking to protect customer and employee data, a non-profit organization managing sensitive information, or an individual seeking robust data security, ALTCHA Forms provides the tools and features necessary to meet your needs. With a focus on compliance, user-friendly design, and advanced security measures, our platform is tailored to support diverse users in navigating complex regulatory landscapes and ensuring data protection.
SharkEyes.dev's answer:
Web developers, SaaS founders, indie hackers, and digital agencies looking for an easy-to-integrate, privacy-centric alternative to reCAPTCHA or hCaptcha for protecting lead forms, signups, and feedback channels.
SharkEyes.dev's answer:
SharkEyes was created out of frustration with complex, user-unfriendly captchas that hurt site conversions and compromise visitor privacy. We wanted a lightweight, modern security solution that protects forms effectively without forcing real users to solve puzzles or giving away their personal browsing data.
Share your experience with using ALTCHA and SharkEyes.dev. For example, how are they different and which one is better?
Recommendations tracked on public social media and blogs since March 2021.


The captcha on orkestr is Altcha. Self-hosted, no third-party JS, no Google, no behavioral tracking. Users don't see a puzzle. There's a single checkbox and a quiet "verifying..." while the browser does some math. About a second, total. - Source: dev.to / 4 months ago
Here's how PoW works for form protection (using the ALTCHA wire format):. - Source: dev.to / 6 months ago
Go based, similar to JS based ALTCHA https://altcha.org/ discussed at https://news.ycombinator.com/item?id=43971068. - Source: Hacker News / 9 months ago
Tracking SharkEyes.dev since Sep 2026.
When comparing ALTCHA and SharkEyes.dev, you can also consider the following products.

reCAPTCHA is a free security service that protects your websites from spam and abuse.
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Do you use a captcha to keep out bots? hCaptcha is a drop-in replacement for reCAPTCHA that earns website owners money and helps companies get their data labeled.
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Cloudflare's service for any company to replace CAPTCHAs and deliver a better experience to web visitors.
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Akismet is a spam fighting service that protects millions of WordPress sites from comment and contact form spam.
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Independent, privacy-first, self-hostable CAPTCHA service made in EU
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A reliable captcha service, offers advanced security to protect websites from spam and abuse while ensuring a user-friendly experience for legitimate visitors.
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