---
title: utf8.is_valid
summary: null
url: >-
  https://www.fastly.com/documentation/reference/vcl/functions/unicode/utf8-is-valid
---

```
BOOL utf8.is_valid(STRING s)
```

**Available in:** all subroutines

Returns `true` if the string `s` contains valid UTF-8 and returns `false` if it 
does not contain valid UTF-8. An empty string is considered valid.