traefik/docs/content/middlewares/http/stripprefixregex.md
2022-04-15 15:44:08 +02:00

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---
title: "Traefik StripPrefixRegex Documentation"
description: "In Traefik Proxy's HTTP middleware, StripPrefixRegex removes prefixes from paths before forwarding requests, using regex. Read the technical documentation."
---
# StripPrefixRegex
Removing Prefixes From the Path Before Forwarding the Request (Using a Regex)
{: .subtitle }
Remove the matching prefixes from the URL path.
## Configuration Examples
```yaml tab="Docker"
labels:
- "traefik.http.middlewares.test-stripprefixregex.stripprefixregex.regex=/foo/[a-z0-9]+/[0-9]+/"
```
```yaml tab="Kubernetes"
apiVersion: traefik.containo.us/v1alpha1
kind: Middleware
metadata:
name: test-stripprefixregex
spec:
stripPrefixRegex:
regex:
- "/foo/[a-z0-9]+/[0-9]+/"
```
```yaml tab="Consul Catalog"
- "traefik.http.middlewares.test-stripprefixregex.stripprefixregex.regex=/foo/[a-z0-9]+/[0-9]+/"
```
```json tab="Marathon"
"labels": {
"traefik.http.middlewares.test-stripprefixregex.stripprefixregex.regex": "/foo/[a-z0-9]+/[0-9]+/"
}
```
```yaml tab="Rancher"
labels:
- "traefik.http.middlewares.test-stripprefixregex.stripprefixregex.regex=/foo/[a-z0-9]+/[0-9]+/"
```
```yaml tab="File (YAML)"
http:
middlewares:
test-stripprefixregex:
stripPrefixRegex:
regex:
- "/foo/[a-z0-9]+/[0-9]+/"
```
```toml tab="File (TOML)"
[http.middlewares]
[http.middlewares.test-stripprefixregex.stripPrefixRegex]
regex = ["/foo/[a-z0-9]+/[0-9]+/"]
```
## Configuration Options
### General
The StripPrefixRegex middleware strips the matching path prefix and stores it in a `X-Forwarded-Prefix` header.
!!! tip
Use a `stripPrefixRegex` middleware if your backend listens on the root path (`/`) but should be exposed on a specific prefix.
### `regex`
The `regex` option is the regular expression to match the path prefix from the request URL.
For instance, `/products` also matches `/products/shoes` and `/products/shirts`.
If your backend is serving assets (e.g., images or JavaScript files), it can use the `X-Forwarded-Prefix` header to properly construct relative URLs.
Using the previous example, the backend should return `/products/shoes/image.png` (and not `/images.png`, which Traefik would likely not be able to associate with the same backend).
!!! tip
Regular expressions and replacements can be tested using online tools such as [Go Playground](https://play.golang.org/p/mWU9p-wk2ru) or the [Regex101](https://regex101.com/r/58sIgx/2).
When defining a regular expression within YAML, any escaped character needs to be escaped twice: `example\.com` needs to be written as `example\\.com`.