URL Rewrite rules appear to be redirecting instead of rewriting

Question

I am using IIS URL Rewrite 2.0 module to create a URL that always points to the latest version of my app. I have configured it as follows:

<rule name="Latest" stopProcessing="true">
    <match url="^latest(.*)" />
    <action type="Rewrite" url="1.1{R:1}" />
</rule>

The intention is that if something goes to /latest/* then all of the URLs are rewritten as /1.1/*. For example /latest/index.html should become /1.1/index.html.

This is working when I request a file, for example:

/latest/index.html - works
/latest/js/app.js - works

However this does not work:

/latest

Since index.html is the default document, I would expect this to rewrite to /1.1/index.html, but in fact it seems to do a redirect. For example, if I type the following in the browser address bar:

http://<domain>/latest

and press ENTER, it changes to:

http://<domain>/1.1

as if redirected. It still works, but I don't want the URL to change (hence why I'm using Rewrite rather than Redirect). Any idea why? Is there something wrong my rule?

Salman A · Answer 1 · 2015-04-29T19:05:15.753

When you request the URL /latest your rules rewrites it to /1.1. Since /1.1 matches an existing directory instead of a file, IIS responds with a courtesy redirect as described here. IIS uses the rewritten URL since it cannot see the original URL.

Instead of serving same content through two URLs (/latest and /latest/) I would suggest that you emulate the same behavior through your rules. If the requested URL is /latest it should first redirect to /latest/ then rewritten:

<rule name="Latest: force trailing slash" stopProcessing="true">
    <match url="^latest$" />
    <action type="Redirect" url="latest/" redirectType="Found" />
</rule>
<rule name="Latest: rewrite" stopProcessing="true">
    <match url="^latest/(.*)" />
    <action type="Rewrite" url="1.1/{R:1}" />
</rule>

Yes, you're right. I've included this along with Kev's answer and it's now behaving how I'd like. Thanks! — Barguast, Apr 29 '15 at 18:00

Kev · Accepted Answer · 2015-04-29T17:36:26.027

This is likely the problem you're experiencing:

IIS generates courtesy redirect when folder without trailing slash is requested

(Although that article is about IIS6, IIS7+ behaves in the same way and it seems you can't disabled this behaviour.)

Add a rule before your existing one that matches just /latest (no trailing slash):

<rewrite>
    <rules>
        <rule name="Latest1" stopProcessing="true">
            <match url="^latest$" />
            <action type="Rewrite" url="1.1/" />
        </rule>
        <rule name="Latest2" stopProcessing="true">
            <match url="^latest(.*)" />
            <action type="Rewrite" url="1.1{R:1}" />
        </rule>
    </rules>
</rewrite>

There's probably a more elegant way, that does what it says on the tin.

You may need to do a hard reload of the page because your browser may cache the redirect, you can always test in "incognito mode" which never saves permanent redirects between sessions.

Thanks, it appears to work to a degree, except all of the resources referenced in the index.html appear to be loaded from the wrong URL. For example, if I go to /latest then a — Barguast, Apr 29 '15 at 17:48
Disregard the previous comment - I think Salman A explained and resolved this too. — Barguast, Apr 29 '15 at 18:00

URL Rewrite rules appear to be redirecting instead of rewriting

2 Answers2