FCaptcha review
An open-source CAPTCHA with multiple bot-detection methods and compatible verification endpoints.
Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
FCaptcha is an open-source CAPTCHA project for teams protecting forms, logins, registrations and other high-value actions. It is aimed especially at developers who want to self-host a verification service and connect it to existing applications. The project provides Go, Python and Node.js server implementations, plus a browser widget. Its modes include a single-click checkbox, invisible background analysis and proof-of-work challenges, giving teams different ways to add verification to user flows.
Detection combines behavioral and environmental signals, including keystroke analysis, headless-browser and automation-framework detection, and vision AI agent detection. SHA-256 proof-of-work adds another challenge type. Compatibility with Turnstile, reCAPTCHA and hCaptcha siteverify endpoints is relevant for teams adapting an existing integration, while listed integrations also include Statamic and Gitea. FCaptcha is MIT-licensed and free as a self-hosted project. These capabilities make it a fit for developers who want control over CAPTCHA processing and are prepared to operate it on their own infrastructure; teams seeking a managed CAPTCHA service should assess that operational distinction before choosing it.
Privacy controls include documented data collection and retention behavior, and the project describes accessibility testing against WCAG 2.2 AA criteria. A notable constraint is that FCaptcha does not provide audio challenges, which may matter to teams evaluating challenge options for accessibility. The listed SDK platform is web, so buyers with needs beyond that scope should check implementation fit. Email and documentation are the stated support channels. FCaptcha suits teams comfortable integrating server-side components and managing their deployment; organizations needing audio challenges or a broader SDK platform scope should consider alternatives.
FCaptcha pros and cons
- Where it wins
- Offers checkbox, invisible and SHA-256 proof-of-work modes
- Detects automation and vision AI agents using behavioral and environmental signals
- Includes Turnstile-, reCAPTCHA- and hCaptcha-compatible verification endpoints
- Where it doesn't
- Does not offer audio challenges
- The listed SDK platform is web
- Self-hosting keeps processing on the operator’s infrastructure
FCaptcha fact sheet, pricing and score →
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