---
title: accept.charset_lookup
summary: null
url: >-
  https://www.fastly.com/documentation/reference/vcl/functions/content-negotiation/accept-charset-lookup
---

```
STRING accept.charset_lookup(STRING requested_charsets, STRING default, STRING accept_header)
```

**Available in:** all subroutines

Selects the best match from a string in the format of an `Accept-Charset` 
header's value in the listed character sets using the algorithm described in 
Section 5.3.3 of 
[RFC 7231](https://httpwg.org/specs/rfc7231.html#rfc.section.5.3.3).

This function takes the following parameters:

1. a colon-separated list of character sets available for the resource,
2. a fallback return value,
3. a string representing an `Accept-Charset` header's value.

## Example

```vcl
set bereq.http.Accept-Charset =
  accept.charset_lookup("iso-8859-5:iso-8859-2", "utf-8",
    req.http.Accept-Charset);
```