---
title: querystring.regfilter
summary: null
url: >-
  https://www.fastly.com/documentation/reference/vcl/functions/query-string/querystring-regfilter
---

```
STRING querystring.regfilter(STRING url, REGEX pattern)
```

**Available in:** all subroutines

Returns the given URL without the parameters matching a regular expression. 
Groups within the regular expression are treated as if they were written as 
non-capturing groups. For example:

```vcl
if (req.url.qs ~ "key-(?:[0-9]|\w)=(.*)-(.*)") { # captures to re.group.1 and re.group.2
  set req.url = querystring.regfilter(req.url, "key-([0-9]|\w)"); # does not capture
  set req.http.X-Key-1 = re.group.1;
  set req.http.X-Key-2 = re.group.2;
}
```

The `"key-([0-9]|\w)"` pattern shown here behaves as if it were written as a 
non-capturing group, `"key-(?:[0-9]|\w)"`, ensuring the contents of 
`re.group.1` and `re.group.2` are not affected by the call to 
`querystring.regfilter()`.

## Example

```vcl
set req.url = querystring.regfilter(req.url, "utm_.*");
```