OmniCaptcha
One server-side API for seven CAPTCHA providers. Fail-closed verification for Rust.
OmniCaptcha gives a Rust backend one request, verdict, policy, and error model across Cloudflare Turnstile, hCaptcha, reCAPTCHA, Friendly Captcha, CaptchaFox, MTCaptcha, and ALTCHA. Each provider sits behind a Cargo feature and none is enabled by default, so a build carries only what it uses.
Verification is fail-closed: an unavailable or ambiguous provider never turns into an accepted verdict. Policy checks for action, hostname, score, challenge age, and site key run locally, retries account for single-use tokens, and tokens and credentials stay redacted.
It is published on crates.io as captcha-sdk.