# Effect 4.0 Ships: Dependency-Free Rewrite with 5x Smaller Bundles and Long-Term Support > Source: > Published: 2026-11-10 06:33:00+00:00 [Effect](https://effect.website/), the TypeScript framework for building production-grade applications with typed errors, structured concurrency and dependency injection, has [released Effect 4.0](https://effect.website/blog/releases/effect/40). Published on 30 September 2026, it is the first stable version of a line that spent eight months in beta and six weeks in release candidate. Effect 4.0 is a from-scratch rewrite of the fiber runtime, aimed at smaller bundles, lower memory use and higher throughput. The team's own figures put a minimal program using Effect, Stream and Schema at [7.1 kB against 35.6 kB in 3.x](https://effect.website/blog/releases/effect/40), a 5x reduction. The heap used by 50,000 fibers drops from 157.5 MB to 21.8 MB, an 86% cut, and concurrent task throughput moves from 0.71 million to 4.57 million tasks per second, roughly 6.4x. The numbers are medians of nine fresh-process runs on identical source, and as [noted by stork.ai](https://www.stork.ai/blog/effect-40-is-powerfuland-riskier-than-it-looks), have not been independently reproduced. Alongside the rewrite, the ecosystem has been consolidated. Core modules from `@effect/platform`, `@effect/rpc` and `@effect/cluster` now live inside the main `effect` package, every `@effect/*` package shares a single version, and the core ships with zero runtime dependencies after the final removal of `pg` (replaced by a native `PgProtocol` client) and MessagePack. With 4.0, the team has introduced a long-term support policy. Effect 4.x receives bug fixes until September 2029, or one year after 5.0 ships, whichever is later. Security fixes run until September 2029 or two years after 5.0, again whichever is later. [Stork.ai](https://www.stork.ai/blog/effect-40-is-powerfuland-riskier-than-it-looks) points out that the 43.9 million weekly downloads cited at launch covers the whole ecosystem across beta and RC tags, while stable Effect 4.0 itself recorded "approximately 150,000 downloads on its first day". On HackerNews, one commenter has been using the beta for some time and has had a very positive experience: I’ve been using the beta on three separate projects for quite a while now and it has been totally pain-free. I mostly use the v3x core library (which has expanded to contain other libraries in v4) and Schema so I can’t speak to much outside of those, but I trust they’ve done a great job all around. I don’t see it mentioned here, but 4 also comes with a much simpler API in some modules. Schema is much better. It’s an exceptional update. I followed many of the video logs on YouTube and was impressed by the team. This is one of my favourite software projects, period. This rebuild is incredibly well done, and I hope a lot of people are willing to try it out and adopt it, especially with the LTS. The team's own [Effect 4.0: The First Week](https://effect.website/blog/effect-4-first-week) post, published alongside patch releases 4.0.1 and 4.0.2 on 8 October, admitted that several modules intended to ship as unstable went out without a `@stability` tag, implicitly promising they were stable. The missing tags were added, and every exported API now declares its stability explicitly. The same window moved HTTP, SQL, RPC and AI spans to the OpenTelemetry semantic conventions. [Effect 4.1](https://effect.website/blog/releases/effect/41) followed on 20 October 2026 with new `effect/crypto` modules covering randomness, hashing and signing, a `Glob` module backed by `FileSystem.glob` on Node, Bun and Deno, a streaming `Csv` module in `effect/encoding`, and support for [RFC 9457 Problem Details](https://www.rfc-editor.org/rfc/rfc9457) in `HttpApi`. For teams on 3.x, the [v3 to v4 migration guide](https://github.com/Effect-TS/effect/blob/main/MIGRATION.md) is the starting point, with the team suggesting coding agents can handle most of the mechanical work. Effect sits in similar territory to [ZIO](https://zio.dev/) in the Scala world, alongside TypeScript libraries such as [Effection 4.0](https://frontside.com/effection) that target structured concurrency with a deliberately smaller surface. Effect is an open-source TypeScript framework maintained by [Effectful Technologies](https://effectful.co/), providing typed error handling, structured concurrency, dependency injection and observability primitives for both frontend and backend applications.