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Response

A builder-like pattern is used to construct an instance of HttpResponse. HttpResponse provides several methods that return a HttpResponseBuilder instance, which implements various convenience methods for building responses.

Check the documentation for type descriptions.

The methods .body, .finish, and .json finalize response creation and return a constructed HttpResponse instance. If this methods is called on the same builder instance multiple times, the builder will panic.


JSON Response​

The Json type allows to respond with well-formed JSON data: simply return a value of type Json<T> where T is the type of a structure to serialize into JSON. The type T must implement the Serialize trait from serde.

For the following example to work, you need to add serde to your dependencies in Cargo.toml:

[dependencies]
serde = { version = "1.0", features = ["derive"] }

Using the Json type this way instead of calling the .json method on a HttpResponse makes it immediately clear that the function returns JSON and not any other type of response.

Content encoding​

Actix Web can automatically compress payloads with the Compress middleware. The following codecs are supported:

  • Brotli
  • Gzip
  • Deflate
  • Identity

A response's Content-Encoding header defaults to ContentEncoding::Auto, which performs automatic content compression negotiation based on the request's Accept-Encoding header.


Explicitly disable content compression on a handler by setting Content-Encoding to an Identity value:


When dealing with an already compressed body (for example, when serving pre-compressed assets), set the Content-Encoding header on the response manually to bypass the middleware: