Comparison
CaptchaKit vs ALTCHA: hosted arcade games or open-source proof of work?
Short answer
ALTCHA is an open-source (MIT) proof-of-work CAPTCHA you can self-host, with managed Cloud from EUR 47 a month. CaptchaKit is a hosted arcade-game CAPTCHA that is pay what you want, one time. Choose ALTCHA if you want to run and own the code. Choose CaptchaKit if you want a hosted service with nothing to maintain.
Side by side
CaptchaKit and ALTCHA. Prices as of October 2026.
| Feature | CaptchaKit | ALTCHA |
|---|---|---|
| Entry price | Pay what you want, one time | Yes Open source core, free (MIT) |
| Managed plans | Business $29 a month | Cloud EUR 47 (3 sites), Plus EUR 137 (10), Max EUR 187 (50) a month |
| Self-hosting | Hosted by CaptchaKit, nothing to run | Sentinel Professional EUR 99 a month, Enterprise EUR 799 a month |
| Method | Arcade game and signed one-time token | Proof of work |
| Trial | Public demo page for every game | 30-day free trial on Cloud |
| WordPress | Yes Plugin on wordpress.org | Free plan; Professional EUR 18.90 a month; lifetime EUR 499; Agency EUR 119.90 a month |
| Dashboard and analytics | Paid add-on Business, $29 a month | Paid add-on Cloud and Sentinel plans |
| Team and audit | Paid add-on Business: team seats, two-factor auth, audit logs | Paid add-on Sentinel Enterprise: SSO and audit logs |
| Domains | Yes Unlimited on lifetime access | 3, 10 or 50 sites on Cloud; instances on Sentinel |
The short version
ALTCHA publishes its core under the MIT license and also sells a managed Cloud service and self-hosted Sentinel editions. If you want to read the code, run it yourself and avoid a per-site fee, that is a real advantage.
CaptchaKit is a hosted product. All game code and completion logic is served from captchakit.com, so nothing security-relevant runs on your site, and there is nothing for you to deploy, patch or monitor.
Price and what you run
ALTCHA's pricing page lists the open-source core as free. Cloud starts at EUR 47 a month for 3 sites, EUR 137 for 10 sites and EUR 187 for 50 sites, each with a 30-day trial. Sentinel, the self-hosted edition, is EUR 99 a month for up to 3 instances (Professional) or EUR 799 a month for unlimited instances (Enterprise). The WordPress plugin has a free plan, with Professional at EUR 18.90 a month, a EUR 499 lifetime option and Agency at EUR 119.90 a month. All prices as of October 2026.
CaptchaKit's pricing is pay what you want, one time, for the full pack or a single game, with lifetime access and unlimited domains. Business is $29 a month for analytics, webhooks, team seats, two-factor auth and audit logs.
If you self-host ALTCHA, remember the servers are on you. If you buy CaptchaKit, the hosting is ours.
Different ideas of a challenge
ALTCHA uses proof of work: the visitor's browser spends a little computing effort and the form goes through, usually with no visible step. CaptchaKit uses a game, which is visible, takes 6 to 20 seconds on average depending on the title, and can be themed for your site.
Each has a server step. With CaptchaKit your server posts the pass token to /api/verify with a Bearer API key; tokens are signed, expire in 10 minutes and work once. The docs show Node, Python and PHP versions.
Cookies and privacy
ALTCHA states that it uses no cookies and shares no data with third parties. That is the vendor's statement from its open-source page, so confirm it for your deployment.
CaptchaKit's privacy policy says no advertising or tracking cookies are used, with a session cookie only for account login. It states that it receives the game outcome and a timestamp from your visitors, with no fingerprinting, tracking pixel, behavioral profiling or cross-site tracking. Server logs with IP addresses are kept for up to 90 days.
Where ALTCHA is a good fit
ALTCHA is a good fit for developers and teams who want open-source code, a permissive license and the option to self-host, and for people who want no visible challenge. Its Sentinel edition targets teams with the DevOps capability to run instances, and its Enterprise plan adds SSO and audit logs.
Where CaptchaKit is a good fit
CaptchaKit is a good fit when you want a hosted service, a game your visitors recognize, and a one-time price. Teams that need an accessible alternative path get one built in: a "Can't play? Accessible check" link that switches to a screen-reader-friendly question and issues the same pass token. See CAPTCHA without cookies for a neutral comparison of vendor statements.
Who picks which
A developer who wants to read the code, avoid vendor lock-in and run the verification server: ALTCHA's open-source core is built for that. A small agency that wants to add a branded CAPTCHA to client forms without running anything: CaptchaKit's hosted widget fits. A team with a security questionnaire to answer: both sell paid tiers with audit logs (ALTCHA Sentinel Enterprise, CaptchaKit Business).
ALTCHA's own page says the open-source core has no dashboard, analytics or adaptive risk scoring, which Cloud and Sentinel add. CaptchaKit's dashboard analytics, signed webhooks and audit logs are in Business at $29 a month.
Switching from ALTCHA
Replace the ALTCHA widget element with CaptchaKit's div, add the script tag, and swap your verification code for POST /api/verify. If you were running ALTCHA on your own server, you can retire that server once the cutover is complete. On WordPress use the CaptchaKit plugin instead of the ALTCHA plugin and test login, registration, comments and checkout.
Questions
Is ALTCHA free?
The open-source core is free under the MIT license. Managed Cloud starts at EUR 47 a month and the self-hosted Sentinel at EUR 99 a month (checked October 2026).
Which one needs server maintenance?
Self-hosted ALTCHA does. CaptchaKit is hosted, so you only add the widget and the server-side verify call.
Which is more visible to visitors?
CaptchaKit, because the visitor plays a short game. Proof of work usually runs without a visible step.
Can I use either on WordPress?
Yes. ALTCHA lists a WordPress plugin, and CaptchaKit's plugin covers login, registration, comments and WooCommerce checkout.
How does CaptchaKit check a token?
Your server sends POST /api/verify with the token, your site key and a Bearer API key. You get { "success": true } for a valid, unused token.
Can I try CaptchaKit without commitment?
Every game has a public demo page. Play it and check the widget in your own form before choosing a price.
Sources
- ALTCHA pricing (checked 2026-10-17)
- CaptchaKit documentation (checked 2026-10-17)
- CaptchaKit pricing (checked 2026-10-17)
- CaptchaKit privacy policy (checked 2026-10-17)
- CaptchaKit on WordPress.org (checked 2026-10-17)
- ALTCHA open-source CAPTCHA (checked 2026-10-17)
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