URL rewrite (custom forwarding path)

Azure Front Door supports URL rewrite by allowing you to configure an optional Custom Forwarding Path to use when constructing the request to forward to the backend. By default, if no custom forwarding path is provided, then Front Door will copy the incoming URL path to the URL used in the forwarded request. The Host header used in the forwarded request is as configured for the selected backend. Read Backend Host Header to learn what it does and how you can configure it.

The powerful part of URL rewrite using custom forwarding path is that it will copy any part of the incoming path that matches to a wildcard path to the forwarded path (these path segments are the green segments in the example below):
Azure Front Door URL Rewrite

URL rewrite example

Consider a routing rule with the following frontend hosts and paths configured:

Hosts Paths
www.contoso.com /*

The first column of the table below shows examples of incoming requests and the second column shows what would be the "most-specific" matching route 'Path'. The third and subsequent columns of the first row of the table are examples of configured Custom Forwarding Paths, with the rest of the rows in those columns representing examples of what the forwarded request path would be if it matched to the request in that row.

For example, if we read across the second row, it's saying that for incoming request www.contoso.com/sub, if the custom forwarding path was /, then the forwarded path would be /sub. If the custom forwarding path was /fwd/, then the forwarded path would be /fwd/sub. And so forth, for the remaining columns. The emphasized parts of the paths below represent the portions that are part of the wildcard match.

Incoming request Most-specific match path / /fwd/ /foo/ /foo/bar/
www.contoso.com/ /* / /fwd/ /foo/ /foo/bar/
www.contoso.com/sub /* /sub /fwd/sub /foo/sub /foo/bar/sub
www.contoso.com/a/b/c /* /a/b/c /fwd/a/b/c /foo/a/b/c /foo/bar/a/b/c
www.contoso.com/foo /foo / /fwd/ /foo/ /foo/bar/
www.contoso.com/foo/ /foo/* / /fwd/ /foo/ /foo/bar/
www.contoso.com/foo/bar /foo/* /bar /fwd/bar /foo/bar /foo/bar/bar

Optional settings

There are additional optional settings you can also specify for any given routing rule settings:

  • Cache Configuration - If disabled or not specified, then requests that match to this routing rule will not attempt to use cached content and instead will always fetch from the backend. Read more about Caching with Front Door.

Next steps