🆚 Altcha vs. Cap
- 📈 Altcha is much more popular than Cap.
- 🌍 Altcha is more popular in all countries.
- ⭐ Cap is particularly popular in Chile.
Altcha
CapType
About
Altcha is an open-source, privacy-first, self-hosted captcha alternative that uses a proof-of-work mechanism to protect websites, APIs, and online services from spam and unwanted content.
It performs client-side computational challenges based on hashing and memory-hard algorithms such as Argon2 and Scrypt, adds headers and signatures for verification, operates without cookies, fingerprinting, or external requests, and supports more than 50 languages to meet accessibility and privacy requirements.
Cap is an open-source, self-hosted 
reCAPTCHA alternative that verifies visitors without visual puzzles, tracking, or third-party services.
It uses a two-layer verification model that combines proof-of-work challenges accelerated with 
WebAssembly and Web Workers, including SHA-256 hashing and optional GPU-resistant time-locks.
Headquarters
Pricing
Categories
Popularity
Determined by the number of sites using each technology.
Market share
Popularity by country
Determined by the number of sites detected from each country.
Awards
- ⭐ 4th most popular in the Netherlands in the Captchas category.
- ⭐ 4th most popular in France in the Captchas category.
- ⭐ 4th most popular in Switzerland in the Captchas category.
- ⭐ 5th most popular in Germany in the Captchas category.
- ⭐ 5th most popular in the United States in the Captchas category.
Popularity by domain category
Determined by the number of sites in each category.
Top sites
Top-ranked sites that use these technologies.
Compare alternatives
Technologies with similar characteristics.
🗃️ About This Data
- We evaluate the popularity of technologies based on the number of websites where we detect their usage.
- Technologies without a detectable web footprint, and those we do not track, are not reflected in the calculated market share.
- This report is based on the analysis of 3,814,833 websites.
- Statistics were last calculated on .
- For more details, see our methodology and disclaimer.