We are very pleased to announce v4.0 of Actix Web! Actix Web, written in Rust, is a powerful, high-performance web framework used to create web services, from micro to monolith. You can rely on it to build your most mission-critical systems.

The v4 release have been a community-driven effort, with of over 600 commits by 57 contributors! We've come a long way together. Key changes include:

• Full compatibility with Tokio v1 ecosystem including #[tokio::main] support.
• Make actix-http more lean. This crate underpins Actix Web, containing our HTTP/1 implementation and lower-level HTTP handling.
• API refinements, generally to increase expressiveness and developer productivity.
• Reducing the number of paper-cuts and non-obvious behavior in specific APIs.
• Vastly improved documentation on a large number of key items.

The migration guide contains explanations and diffs showing how to update. It is worth reading at least the items marked with a warning emoji because these show behavioral changes and will not surface compiler errors. Changelogs for actix-http and actix-web contain the complete, exhaustive list (~400 entries) of changes.

The team learned a lot while working towards this release. Expect shorter beta periods between releases.

The other crates in the actix-web ecosystem will be stabilized in the next few days.

The first couple of point releases for the v4 cycle are largely planned out. Many of the items slated for inclusion are already available in the actix-web-lab crate.