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Glossary entry

FunCaptcha (Arkose Labs)

FunCaptcha is the puzzle-based CAPTCHA from Arkose Labs Enterprise. Rotation, image-pick, and 3D match challenges; used by Microsoft, Roblox, Twitter.

Definition

FunCaptcha is the puzzle-based CAPTCHA product from Arkose Labs (formerly the standalone FunCaptcha company; rebranded as Arkose Labs Enterprise). Visitors solve a small interactive puzzle — rotate the animal to face up, pick the matching shape, line up the 3D objects — that's computationally expensive to brute-force but easy for humans.

How it works

The widget loads from client-api.arkoselabs.com (or a customer-specific subdomain), fetches a session blob, and renders the puzzle. The puzzle variant is chosen dynamically per-session based on Arkose's scoring layer — low-friction users get a 2-second easy puzzle, high-friction users get the harder 3D match. On success, Arkose returns a token of the form fc-<base64>; the site posts {token, secret} to verify-api.arkoselabs.com/verify. Enterprise deployments additionally pass an encrypted "data blob" that binds the token to a backend session context.

Where you see it

Microsoft account signup, Roblox, Twitter/X login flows, dating apps, high-value e-commerce. Often the fallback when other CAPTCHA solutions are bypassed too easily.

Try the API See pricing

Frequently asked questions

Puzzles burn ~5 seconds of compute per solve, making mass automation expensive even for AI solvers. Scoring-only solutions are cheap to bypass at scale; puzzle solving rate-limits attackers economically.

Yes, with ~10–20 seconds per puzzle depending on the variant. Rotation and image-pick are faster than the 3D match-the-shape variant introduced in 2023.

It's an Arkose Enterprise feature: the page generates an encrypted context blob and includes it in both the puzzle setup and the verify call. The token is bound to the blob, preventing token replay across sessions.

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