Effect

Effect is a TypeScript ecosystem for building reliable, production-ready software. Its core library brings common application needs together in one cohesive runtime, helping teams manage complexity as systems grow without adding a separate package for every problem. Developers describe programs with explicit success types, typed errors, and declared dependencies, so code is easier to reason about, test, and maintain.

Effect offers tools for structured concurrency, dependency injection, scheduling, retries, resource cleanup, and unified schemas for runtime validation, serialization, and API contracts. It also supports observability through tracing, structured logging, and metrics. These capabilities help teams handle failures and asynchronous work more deliberately, while making dependencies and potential errors visible in the type system.

The project provides documentation, a blog, a podcast, community support, talks, and learning resources, including guidance for writing Effect with AI coding tools. It can be adopted incrementally in existing TypeScript codebases by wrapping current asynchronous APIs and refactoring gradually. Effect is used in production by organizations including OpenCode, MasterClass Cortex, and OpenRouter.