An SDK for every layer of your stack

Device-scoped flag fetching with a durable local cache: every read falls back to the last value this device saw, then false - and it mints the stable, privacy-respecting device identity that per-device billing counts, shared across your app family and never derived from hardware identifiers.

The same durable cache and fail-safe cascade, native to Kotlin: isEnabled and friends never throw. It follows the same cross-platform device-identity contract as iOS - one random, pseudonymous identifier, never derived from hardware IDs.

Zero-dependency TypeScript for browsers: no call throws and no promise rejects - outages, dead networks and ad blockers all resolve to a value. Browsers that declare navigator.webdriver automation are served but never billed.

Polls the ruleset export with an ffs_ server key and evaluates flags locally, in-process - no network hop per flag check, and evaluation never returns an error and never panics.

The same contract and local evaluation, in TypeScript. ESM-only with zero runtime dependencies - and CommonJS on Node 22+ can still require() it. The poller never keeps your process alive after your code finishes.

Pure standard library, and a synchronous API that is safe inside asyncio apps - evaluation is an in-memory read, nothing to await. The poller is a daemon thread and never blocks interpreter exit.

Zero dependencies including JSON - the bounded parser lives in the SDK, so nothing new enters your dependency tree. Getters like boolValue never throw, and the daemon poller never blocks JVM exit.