# Content-Language header

> Describes the natural language(s) of the intended audience for the message body.

Source: https://apiguide.dev/headers/content-language
Direction: both
Registered: yes
Defined in: RFC 9110, Section 8.5 <https://www.rfc-editor.org/rfc/rfc9110.html#section-8.5>
Updated: 2026-07-10

## What is the Content-Language header?

The `Content-Language` header states the natural language(s) that the representation body is intended for, using language tags such as `en`, `en-US`, or `fr-CA`. It describes the audience, not necessarily every language present in the content.

## API Usage & Best Practices

* **Pair with `Accept-Language`**: Use it to confirm which language variant was returned in response to a client's `Accept-Language` preferences.
* **Support content negotiation**: Set it on localized API responses so clients and caches can distinguish between language variants of the same resource.
* **Multiple tags allowed**: A comma-separated list can indicate content intended for several audiences at once.

## Examples

```http
HTTP/1.1 200 OK
Content-Type: application/json
Content-Language: en-US
```