# Rewriting of headers

Because we are based on [Varnish](https://www.varnish-software.com/) Enterprise software, Transparent Edge offers great flexibility when it comes to changing your website’s default behavior. 

Rewriting headers is very common and rather easy to do. The most typical cases are:

#### Rewriting the Host header

The typical use case:

```javascript
sub vcl_recv{
  if ((req.http.host == "www.transparentcdn.com") && (bereq.url ~ "/blog")) {
    set http.host == "blog.transparentcdn.com"
    set req.backend_hint = c83_tcdn.backend();
  }
}
```

#### Rewriting the Cache-Control header

```javascript
sub vcl_backend_response {
     if ((bereq.http.host == "www.transparentcdn.com") && (bereq.url ~ "/my-new-url")) {
            set beresp.http.Cache-Control = "max-age=0, s-maxage=10";
            set beresp.ttl = 10s;
    }
}
```

#### Deleting headers

Based on the previous example, we can erase the Cache-Control header that comes from the origin before forcing the cache time.

```javascript
sub vcl_backend_response {    
    if ((bereq.http.host == "www.transparent.com") && (bereq.url ~ "/my-new-url")) {
            unset beresp.http.Cache-Control;
            set beresp.http.Cache-Control = "max-age=0, s-maxage=10";
            set beresp.ttl = 10s;
    }
}    
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.transparentedge.eu/getting-started/faq/features/reescritura-de-cabeceras.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.