Cap

Cap vs Anubis ​

Anubis is a proof-of-work scraper deterrent, popular in self-hosted communities for blocking AI training crawlers and aggressive scrapers at the edge. It and Cap share the proof-of-work core, but they're aimed at different problems.

Quick verdict ​

Use Anubis when you want to gate an entire site or path against bots and scrapers at the reverse-proxy level — usually because crawlers are eating your bandwidth. Use Cap when you want to gate a specific action — a form submission, an API call, an account creation — and let normal browsing continue freely.

Where Anubis makes sense ​

  • You want to put a PoW wall in front of an entire site or sub-path.
  • The threat model is mass scraping or bot-driven request floods at the edge.
  • You're comfortable making every visitor solve a small challenge before any page loads.

Where Cap is the better choice ​

  • Per-action protection, not per-pageview. Cap protects forms, signups, contact pages, and API endpoints — exactly where abuse converts to cost. Visitors browse normally.
  • Difficulty is per-action. Anubis's challenge has to be small enough not to hurt every page load, which limits how high you can crank it. Cap is configured per-action, so difficulty can be set higher on signup or login forms without hurting browsing.
  • Two verification layers. Cap layers instrumentation challenges on top of PoW, so even bots that bring GPU-acceleration to the proof-of-work step still have to fake a real browser environment.
  • Standalone server with a dashboard. Cap ships analytics, multi-site-key management, and a reCAPTCHA-compatible siteverify endpoint out of the box.
  • Widget UX. Cap is meant to be visible to humans on a form — there's a checkbox, progress indicator, and brand surface. Anubis is a transparent gate.

They can coexist ​

If you're already running Anubis in front of a site for crawler protection, you can still use Cap on individual high-value forms and API endpoints inside that site. The two solve different problems and don't conflict.

See also ​