
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.

The modern platform for creating, sharing, and collaborating on AI prompts. Advanced version control and real-time testing.

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 | diffyn.com |
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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...
No description of Diffyn yet.
What each product offers, as listed by its team.


An editorial look at what each product does well and who it suits.


No analysis of ALTCHA yet.
Overall verdict
Why this product is good
Recommended for
Walkthroughs and reviews on video.
No ALTCHA videos yet. You could help us improve this page by suggesting one.
The Ultimate Prompt Tool for Creators – Visualize & Organize with Diffyn
How often each product is chosen within a category, 0–100% relative to the other.


As answered by people managing ALTCHA and Diffyn.
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.
Diffyn's answer:
Addresses workflow and change management on LLM prompts, provide teams with traceability and visualization of tests across multiple models, provide deeper understading into efficiency of these prompts.
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.
Diffyn's answer:
Diffyn is the platform that specializes on both change management and multi-model analysis.
ALTCHA's answer
JavaScript and Svelte.
Diffyn's answer:
React, Next.js, POSTGRESQL
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.
Diffyn's answer:
Professionals incorporating LLMs or AI tools in their workflow and wants to keep track of changes and test their prompts.
Diffyn's answer:
I started working on Diffyn when I notice that prompting has become an essential part of work across many industries. While there are version control platofrms like github, they are not designed for just prompt management are can be overkill such applications, it is also not integrated natively with various LLMs and relevant tools for users to validate ideas and visualise results properly.
Share your experience with using ALTCHA and Diffyn. 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 / 5 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 / 10 months ago
Tracking Diffyn since Jun 2025.
When comparing ALTCHA and Diffyn, 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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