Alternatives to Cap

CAPTCHA	Open-source	Free	Private	Fast to solve	Easy for humans	Small error rate	Checkpoint support	Widget support	GDPR/CCPA Compliant	Customizable	Hard for bots	Easy to integrate
Cap	✅	✅	✅	✅	✅	✅	✅	✅	✅	✅	🟨	✅
Cloudflare Turnstile	❌	✅	🟨	🟨	✅	❌	🟨	✅	✅	❌	🟨	✅
reCAPTCHA	❌	🟨	❌	✅	❌	🟨	❌	✅	🟨	❌	❌	✅
hCAPTCHA	❌	🟨	🟨	❌	❌	🟨	❌	✅	🟨	❌	🟨	✅
Altcha	✅	✅	✅	✅	✅	✅	❌	✅	✅	✅	🟨	🟨
FriendlyCaptcha	❌	❌	✅	🟨	✅	✅	❌	✅	✅	✅	🟨	🟨
MTCaptcha	❌	🟨	🟨	❌	❌	🟨	❌	✅	✅	❌	❌	🟨
GeeTest	❌	❌	❌	🟨	🟨	🟨	❌	✅	✅	❌	🟨	🟨
Arkose Labs	❌	❌	❌	❌	❌	❌	❌	❌	✅	🟨	❌	❌

Note: "Hard for bots" does not consider solvers like 2captcha, XEvil solver, or BrightData, as I cannot verify their legitimacy myself. However, they're extremely cheap.

All alternatives

Cloudflare Turnstile

Cloudflare Turnstile is a great alternative to Cap, but unfortunately it is known for having an extremely high error rate and relies a lot on fingerprinting, especially for users using private browsers such as Brave or Librewolf. Also, unlike Turnstile, Cap is open-source and self-hosted.

reCAPTCHA

Not only is Cap significantly smaller and faster than reCAPTCHA, it's open-source, fully free and is significantly more private. Cap doesn't require you to check traffic signs or solve puzzles, and it doesn't track users or collect data. reCAPTCHA is also highly inefficient due to its challenges being easily solved by multi-modal LLMs like Gemini 2.5

hCAPTCHA

Pretty much the same as reCAPTCHA, although hCAPTCHA is significantly more secure. Personally it's the best alternative to Cap, even though the widget's bundle size alone is significantly bigger.

Unfortunately, hCAPTCHA is extremely expensive to use. At the time of writing, it's $1/1k solutions

Altcha

Cap is slightly smaller than Altcha and includes extra features like checkpoints, progress tracking, and a simpler dashboard. if you don’t need those and prefer a more mature solution, Altcha is a still a solid choice.

mCAPTCHA

mCAPTCHA is similar to both Cap and Altcha, but unfortunately mCAPTCHA doesn't look actively maintained anymore (the last commit was over a year ago).

Its bundle is also significantly larger, with the widget iframe being at 250kb! (150kb of that is just for a shield png)

FriendlyCaptcha

Unlike FriendlyCaptcha, Cap is free and open-source (FriendlyCaptcha is €39/month for 5,000 requests and 5 domains) and has a smaller bundle size.

MTCaptcha

Cap is more lightweight, doesn't rely on users solving an image puzzle that LLMs and OCR can easily solve and is open-source and self-hostable.

GeeTest

Cap is free, self-hosted and open-source, while GeeTest is a paid service. Cap is also more private and doesn't rely on tracking users or collecting data. GeeTest is also china-based, which means that it has to hand over data to the chinese government if they request so. Note that GeeTest partially uses MD5 PoW too.

Arkose Labs

Even while being extremely hard, slow and annoying for humans to solve, Arkose's FunCAPTCHA can be easily solved by LLMs due to their audio CAPTCHA. It's also closed-source and paid.

Anubis

Anubis is quite different from typical captchas. It's mainly designed to block scraping (like Cap's checkpoints) but afaik lacks widget support and customizable server-side integration. It's also not very secure, since its default difficulty is low and easy to bypass.

Its implementation has performance issues too. Anubis runs slower than necessary because it doesn’t use WebAssembly at all (unlike Cap). As such, both the default difficulty and the difficulty usually set by other websites is low to avoid frustrating users. That makes it easier for attackers to use optimized algorithms to solve it quickly.

Plus, the noscript fallback is basically useless: it just makes users wait a few seconds before retrying, which is even weaker than a basic rate limit.