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 0.1% of the captcha market share and is present on 0.02% of all websites.
- 🏠 Website
- </> Source code
GitHub💸 Pricing
Altcha is available in both free and paid versions.
📊 Rankings and Market Share
- Captchas
- Rank: 6
- Market share: 0.1%
- Spam Protection
- Rank: 9
- Market share: 0.1%
🏆 Altcha Awards
- ⭐ 4th most popular in France in the Captchas category.
- ⭐ 4th most popular in the United Kingdom in the Captchas category.
- ⭐ 4th most popular in the Czech Republic in the Captchas category.
- ⭐ 4th most popular in Poland 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 Switzerland in the Captchas category.
- ⭐ 5th most popular in Austria in the Captchas category.
- ⭐ 6th most popular in the Netherlands in the Captchas category.
- ⭐ 7th most popular in France in the Spam Protection category.
⚡ Sites Using Altcha
We have data on 658 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 | #5,726 | Czech Republic | Czech | |
| 2 | #7,004 | Italy | Italian | |
| 3 | #8,664 | United States | English | |
| 4 | #15,520 | United States | American English | |
| 5 | #23,074 | France | English | |
| 6 | #28,030 | Czech Republic | Czech | |
| 7 | #31,089 | Germany | English | |
| 8 | #32,181 | Chile | Spanish | |
| 9 | #39,396 | Germany | German | |
| 10 | #41,874 | English | ||
| 11 | #50,846 | France | French | |
| 12 | #56,968 | Germany | British English | |
| 13 | #58,579 | Brazil | Brazilian Portuguese | |
| 14 | #59,437 | Norway | Norwegian Bokmål | |
| 15 | #66,395 | Russia | Russian | |
| 16 | #66,732 | Russia | Russian | |
| 17 | #78,686 | Chile | Spanish | |
| 18 | #86,966 | Sweden | Swedish | |
| 19 | #87,501 | Czech Republic | Czech | |
| 20 | #94,949 | Czech Republic | Czech |
📈 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, France, and the United States.
- Germany 20.4%
- France 9.8%
- United States 7.5%
- Switzerland 7.2%
- United Kingdom 7%
- Czech Republic 5.7%
- Austria 4.9%
- Netherlands 3.9%
- Poland 3.4%
- Other 30.2%
Most Altcha users speak English, German, or French.
- English 35%
- German 24.6%
- French 10%
- Czech 5.5%
- Spanish 3.6%
- Polish 3.4%
- Dutch 2%
- Swedish 2%
- Italian 1.7%
- Other 12.2%
The Altcha captcha service is especially popular on .com, .de, and .ch top-level domains.
- .com 26%
- .de 14.7%
- .ch 5.3%
- .org 5.2%
- .cz 5%
- .fr 3.3%
- .at 3.3%
- .co.uk 2.1%
- .se 1.7%
- Other 33.4%
The primary market segments for websites utilizing Altcha include business, marketing and merchandising, and online shopping.
- Business 14%
- Marketing/Merchandising 8.2%
- Online Shopping 8.2%
- Non-Profit/Advocacy/NGO 8.2%
- Internet Services 7%
- Education/Reference 7%
- General News 7%
- Real Estate 6.4%
- Software/Hardware 4.7%
- Other 29.3%
🕵️ Similar Technologies
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AWS WAF Captcha💬 Frequently Asked Questions
Where is Altcha's headquarters?
Altcha is located in Brno, Czech Republic.
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 hundreds of sites, including such established ones as cuni.cz,
cultura.gov.it, and
fortiguard.com.
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 7 other captcha services we track.
What are the alternatives to Altcha?
Alternatives and possible competitors to Altcha may include 
reCAPTCHA, 
hCaptcha, and 
Cloudflare Turnstile.
🗃️ 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 3,511,995 websites.
- Statistics were last calculated on .
- For more details, see our methodology and disclaimer.