Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

fix(http): Accept-Encoding can appear in both requests and responses #36657

Open
wants to merge 3 commits into
base: main
Choose a base branch
from
+8 −4
Open

fix(http): Accept-Encoding can appear in both requests and responses #36657

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
0d07450
fix(http): Accept-Encoding can appear in both requests and responses
bsmth Nov 5, 2024
91277bc
Update files/en-us/web/http/headers/accept-encoding/index.md
bsmth Nov 13, 2024
5868683
Merge branch 'main' into 36653-accept-encoding
bsmth Nov 14, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 2 additions & 0 deletions .vscode/dictionaries/terms-abbreviations.txt
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -83,6 +83,7 @@ BMFF
bootup
botmaster
BPTC
Brotli
browserless
BSAC
bytestream
Expand Down Expand Up @@ -880,5 +881,6 @@ yearless
Zalgo
zoomable
ZQSD
Zstandard
ZWNBSP
ZWSP
10 changes: 6 additions & 4 deletions files/en-us/web/http/headers/accept-encoding/index.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,9 @@ browser-compat: http.headers.Accept-Encoding

{{HTTPSidebar}}

The HTTP **`Accept-Encoding`** {{Glossary("request header")}} indicates the content encoding (usually a compression algorithm) that the client can understand. The server uses [content negotiation](/en-US/docs/Web/HTTP/Content_negotiation) to select one of the proposals and informs the client of that choice with the {{HTTPHeader("Content-Encoding")}} response header.
The HTTP **`Accept-Encoding`** {{glossary("request header", "request")}} and {{glossary("response header")}} indicates the content encoding (usually a compression algorithm) that the recipient can understand.
In requests, the server uses [content negotiation](/en-US/docs/Web/HTTP/Content_negotiation) to select one of the encoding proposals from the client and informs the client of that choice with the {{HTTPHeader("Content-Encoding")}} response header.
In responses, it provides information about which encodings are preferred in the content of a subsequent request to the same resource.
bsmth marked this conversation as resolved.
Show resolved Hide resolved

Even if both the client and the server support the same compression algorithms, the server may choose not to compress the body of a response if the `identity` value is also acceptable.
This happens in two common cases:
Expand All @@ -26,7 +28,7 @@ As long as the `identity;q=0` or `*;q=0` directives do not explicitly forbid the
<tbody>
<tr>
<th scope="row">Header type</th>
<td>{{Glossary("Request header")}}</td>
<td>{{Glossary("Request header")}}, {{Glossary("Response header")}}</td>
</tr>
<tr>
<th scope="row">{{Glossary("Forbidden header name")}}</th>
Expand Down Expand Up @@ -64,7 +66,7 @@ Accept-Encoding: deflate, gzip;q=1.0, *;q=0.5
- : A compression format that uses the [Zstandard](https://en.wikipedia.org/wiki/Zstd) algorithm.
- `identity`
- : Indicates the identity function (that is, without modification or compression). This value is always considered as acceptable, even if omitted.
- `*`
- `*` (wildcard)
- : Matches any content encoding not already listed in the header. This is the default value if the header is not present. This directive does not suggest that any algorithm is supported but indicates that no preference is expressed.
- `;q=` (qvalues weighting)
- : Any value is placed in an order of preference expressed using a relative [quality value](/en-US/docs/Glossary/Quality_values) called _weight_.
Expand All @@ -83,7 +85,7 @@ Accept-Encoding: gzip, deflate, br, zstd

### Weighted Accept-Encoding values

The following request header shows `Accept-Encoding` preferences using a quality value between `0` (lowest priority) and `1` (highest-priority).
The following header shows `Accept-Encoding` preferences using a quality value between `0` (lowest priority) and `1` (highest-priority).
Brotli compression is weighted at `1.0`, making `br` the client's first choice, followed by `gzip` at `0.8` priority, and then any other content encoding at `0.1`:

```http
Expand Down