Altcha
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.
According to our data, Altcha is the 6th most popular captcha service on the web.
It has 0.2% of the captcha market share and is present on 0.04% of all websites.
It is especially popular in Germany, appearing on 0.1% of all websites in the country.
- 🏠 Website
- </> Source code
GitHub💸 Pricing
Altcha is available in both free and paid versions.
📊 Rankings and Market Share
- Captchas
- Rank: 6
- Market share: 0.2%
- Spam Protection
- Rank: 9
- Market share: 0.2%
🏆 Altcha 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.
- ⭐ 5th most popular in Austria in the Captchas category.
- ⭐ 7th most popular in the Netherlands in the Spam Protection category.
- ⭐ 7th most popular in the United States in the Spam Protection category.
- ⭐ 7th most popular in France in the Spam Protection category.
- ⭐ 7th most popular in Switzerland in the Spam Protection category.
⚡ Sites Using Altcha
We have data on 1,424 websites that use the Altcha captcha service. Here is a list of some of the top ranked ones.
The highest rated site using Altcha is cuni.cz.
| # | Website | Rank | Country | Language |
|---|---|---|---|---|
| 1 | #5,290 | Czechia | Czech | |
| 2 | #7,616 | Italy | Italian | |
| 3 | #8,928 | Czechia | Czech | |
| 4 | #11,507 | Germany | English | |
| 5 | #15,906 | Sweden | Swedish | |
| 6 | #17,868 | Kenya | English | |
| 7 | #18,687 | United States | English | |
| 8 | #19,303 | Brazil | Brazilian Portuguese | |
| 9 | #25,823 | Brazil | Portuguese | |
| 10 | #29,829 | France | American English | |
| 11 | #29,859 | France | French | |
| 12 | #30,126 | English | ||
| 13 | #33,326 | Costa Rica | English | |
| 14 | #34,667 | France | English | |
| 15 | #38,672 | English | ||
| 16 | #39,690 | Germany | German | |
| 17 | #42,671 | Germany | German | |
| 18 | #59,554 | Sweden | English | |
| 19 | #59,910 | Lithuania | Lithuanian | |
| 20 | #61,154 | Finland | Finnish |
📈 Usage Statistics
Most of the sites that use Altcha:
- are located in Germany
- have content in English
- use the .com domain extension
- fall into the Business category.
Most of the sites using Altcha are from Germany, the Netherlands, and the United States.
- Germany 22.2%
- Netherlands 9.5%
- United States 8.8%
- France 7.7%
- Switzerland 6.5%
- Austria 5.1%
- Czechia 3.5%
- Spain 3.5%
- United Kingdom 3.5%
- Other 29.7%
Most Altcha users speak English, German, or French.
- English 40.6%
- German 23.5%
- French 10.7%
- Spanish 3.6%
- Czech 3.2%
- Polish 2.8%
- Catalan 1.9%
- Dutch 1.7%
- Russian 1.3%
- Other 10.7%
The Altcha captcha service is especially popular on .com, .de, and .ch top-level domains.
- .com 34.6%
- .de 15.7%
- .ch 5.3%
- .org 4.4%
- .at 3.7%
- .cz 2.9%
- .fr 2.9%
- .pl 2.2%
- .net 1.5%
- Other 26.8%
The primary market segments for websites utilizing Altcha include business, marketing and merchandising, and online shopping.
- Business 12.6%
- Marketing/Merchandising 8.9%
- Online Shopping 8.9%
- Real Estate 8.1%
- Internet Services 6.5%
- Education/Reference 6.1%
- General News 6.1%
- Travel 5.7%
- Health 3.6%
- Other 33.5%
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💬 Frequently Asked Questions
Where is Altcha from?
Altcha is from Brno, Czechia.
Can I use Altcha for free?
Yes, there is a free version with limited functionality.
How much does it cost per month?
The pricing starts at €99 per month.
Which country uses Altcha the most?
The majority of Altcha users are from Germany.
Who uses Altcha?
According to our data, Altcha is used on over a thousand sites, including such established ones as cuni.cz,
cultura.gov.it, and
vsb.cz.
Is Altcha used on government websites?
Yes, for example, it is used by cultura.gov.it.
How does Altcha compare to its competitors?
Altcha is a moderately popular captcha service, ranking ahead of 8 other captcha services we track.
🗃️ 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 4,046,631 websites.
- Statistics were last calculated on .
- For more details, see our methodology and disclaimer.