Checkbox, floating or invisible
Show the checkbox, hide it until a button is pressed, or solve in the background from your own code.
The CAPTCHA you host yourself. Bots and AI agents out, people in.
Cap stops scrapers, AI agents and headless browsers with proof-of-work and browser checks. Nobody clicks on buses, and nothing goes to Google.
- agent via Playwright · webdriver_true · blocked
- Firefox 147 on Linux · 1.9 s · passed
- puppeteer-extra-stealth · webdriver_stripped · blocked
- python-requests · no token · rejected
- Safari on iPhone · 2.4 s · passed
- Camoufox · geometry_quantized · blocked
- chrome-headless-shell · chrome_object_missing · blocked
- Canvas Blocker extension · native_tamper · harder puzzle
- HeadlessChrome/142 · headless_token · blocked
- Brave on Windows · 2.1 s · passed
- Selenium + Firefox · webdriver_true · blocked
- curl/8.11 · no token · rejected
- Playwright Firefox · juggler_package · blocked
- Chrome on Android · 3.2 s · passed
- spoofed UA, real one in worker · worker_mismatch · blocked
- LibreWolf · 2.0 s · passed
- CDP viewport override · window_exceeds_screen · blocked
- ungoogled-chromium · 1.8 s · passed
- Firefox via Marionette · webdriver_true · blocked
- Firefox faking Chrome APIs · gecko_contradiction · blocked
- Vivaldi on macOS · 1.7 s · passed
- Go-http-client · no token · rejected
- Firefox on Android · 3.0 s · passed
- GPTBot · no token · rejected
- Opera on Windows · 2.2 s · passed
- node-fetch · no token · rejected
- CDP device emulation · viewport_override · blocked
- Samsung Internet · 2.8 s · passed
- curl · rejected
- Firefox · passed
- Scrapy · rejected
- Safari · passed
- Selenium · blocked
- wget · rejected
- Edge · passed
- Puppeteer · blocked
- httpx · rejected
- Vivaldi · passed
- aiohttp · rejected
- Opera · passed
- Deno fetch · rejected
- Brave · passed
- lynx · rejected
- Chromium · passed
- Go-colly · rejected
- Arc · passed
- Nightmare · blocked
- Zen · passed
jsDelivr served 4,695,114,711 Cap requests in the past year.
Your traffic, on your server
Manage keys, rules, challenges, solves, blocks over time, where they come from, which networks they use and how risky each visitor looked, all locally. Try the interactive demo below.
- Live event log
- Every challenge, solve and block shows up as it happens. Search it by country, network, risk or outcome.
- Rules
- Block, flag or allow a request when it matches conditions you pick.
- Adaptive difficulty
- Visitors who ask too often, or come from networks you pick, get a puzzle up to 10x harder. No paid plan needed.
- Webhooks
- Cap posts to your endpoint on blocks, failed solves, risk flags, AI agents or rule matches.
- Shared lists
- Keep IPs, ranges and networks in lists that rules on every site key can use.
- Share links
- Give someone a read-only view of a key's stats without a dashboard login.
Catches the browsers agents drive
Most abuse now comes from automated browsers, not curl. Cap tests for Playwright, Puppeteer, Selenium, Camoufox and stealth plugins, scores pointer movement and key timing, and spots clicks a script sent.
How detection worksProtection
1,000,000
Automation tools
Puppeteer, Playwright, Selenium and other headless browsers.
Scripted clicks
Clicks and key presses that a script sent instead of a person.
Robotic movement
Mouse paths and typing rhythm that don't look like a person.
AI agents
Browsers that Claude, ChatGPT, Comet and 30 other tools drive for someone.
Claude in Chrome
ChatGPT agent
Comet
Gemini in Chrome
Manus
Codex
Browser Use
GensparkWhat your server gets back from a bot
{ "success": false, "reason": "instr_automated_browser", "blockedBy": [ "webdriver_true", "headless_token" ]}WebDriver flag is set Blocked
The rest of the toolbox
Everything here ships in the open-source release. There is no paid tier holding features back.
Proof-of-work GPUs can't skip
HashWX builds a new hash function for every challenge, so a GPU solves it about 2x faster than a CPU instead of 150x.
HashWXRate limits
Cap how many challenges one IP can ask for in a window, for the whole instance or one site key.
No cookies, no tracking
Nothing goes to a third party, so the privacy review is short in most jurisdictions.
ComplianceAbout 20 kB
The widget weighs about 20 kB minified and gzipped. reCAPTCHA weighs about 500 kB.
Any backend
Verify a token with one POST to /siteverify from any language. The response matches reCAPTCHA's.
Cap has been a good fit for AdGuard. We use it as an invisible, self-hosted CAPTCHA layer with proof-of-work and browser instrumentation challenges, which helps us add abuse protection while keeping the experience lightweight and unobtrusive for regular users.
Head of PR, AdGuardQuestions
More answers in the docsDoes it stop AI scrapers?
Yes. Cap blocks the automated browsers most AI agents browse with, and plain HTTP scrapers can't run the challenge, so they never get a token.
Is it GDPR-friendly?
Yes. Cap doesn't phone home, doesn't set cookies, and doesn't fingerprint users. Your server sees the verification, no one else does.
Can I migrate from reCAPTCHA or hCaptcha?
Yes. Cap's siteverify API is compatible with reCAPTCHA and hCaptcha, but you'll need to swap your client-side code to use Cap's widget.
What does it cost to self-host?
Cap fits on a $5 VPS for most sites. There are no per-request fees, no egress to a third party, and no API quotas to hit.
What is an open-source CAPTCHA?
An open-source CAPTCHA is bot protection whose code you can read, audit, and self-host, rather than a closed third-party service. Cap is licensed under Apache 2.0 and runs entirely on your own infrastructure, so visitor data never reaches a vendor.
Add it to a form this afternoon.
Run one Docker container, create a site key, and drop the widget into your form.
<script src="https://cdn.jsdelivr.net/npm/@cap.js/widget"></script>
<form action="/signup" method="POST">
<input name="email" />
<cap-widget
data-cap-api-endpoint="https://cap.example.com/<site-key>/"
></cap-widget>
<button>Sign up</button>
</form>