IIS Url Rewite: Add Trailing Slash, Preserve Anchors and Query Strings

Question

I've searched several SO posts and haven't found what I'm looking for. It might exists but might be fairly old enough to not show up for me. I found a post (Nginx rewrite: add trailing slash, preserve anchors and query strings) so close to what I need, but it's regex solution does not work for URL Rewrite for IIS, unless I'm doing it wrong.

Problem

I'm trying to add a forward slash / to the end of my url paths while also preserving any existing for query strings ? and anchors #.

Desired Solution

Basically, here's the desired results to each problem:

Entry: https://my.site.com/about
Result: https://my.site.com/about/

Entry: https://my.site.com/about?query=string
Result: https://my.site.com/about/?query=string

Entry: https://my.site.com/about#TestAnchor
Result: https://my.site.com/about/#TestAnchor

Entry: https://my.site.com/about?query=string#TestAnchor
Result: https://my.site.com/about/?query=string#TestAnchor

Current Tests

Our current regex ignores query strings and anchors, but I would like to take them into consideration now.

<rule name="AddTrailingSlash" stopProcessing="true">
  <match url="^([^.?]+[^.?/])$" />
  <action type="Redirect" url="{R:1}/" redirectType="Permanent" />
</rule>

I've also tested another regex but it only works if the url contains both a query string AND an anchor.

<rule name="AddTrailingSlash" stopProcessing="true">
  <match url="^(.*)(\?.*?)(\#.*?)$" />
  <action type="Redirect" url="{R:1}/{R:2}{R:3}" redirectType="Permanent" />
</rule>

NOTE: I just tested this last one (^(.*)(\?.*?)(\#.*?)$) and it actually doesn't work. If the url already contains a / before the ? the test passes which it should not, so I have more work to do here.

Question

Is there a single regex that I can use to solve this or do I need to use multiple rules?

Answer 1

TL;DR

IIS Rewrite (ALL) URIs with Trailing Slash & preserve Fragment and Query Strings

<rule name="AddTrailingSlash" stopProcessing="true">
  <match url="^([^/]+:\/\/[^/#?]+|[^?#]+?)\/?((?:[^/?#]+\.[^/?#]+)?(?:[?#].*)?$)" />
  <action type="Redirect" url="{R:1}/{R:2}" redirectType="Permanent" />
</rule>

IIS use ECMAScript so you can Try it here : https://regexr.com/6ele7

---

Update

IIS Rewrite (Considered) URIs with Trailing Slash & preserve Fragment and Query Strings

<rule name="AddTrailingSlash" stopProcessing="true">
  <match url="^([^/]+:\/\/[^/#?]+|[^?#]+\/[^/.?#]+)([?#].*)?$" />
  <action type="Redirect" url="{R:1}/{R:2}" redirectType="Permanent" />
</rule>

Try it here : https://regexr.com/6fk3g

---

http://127.0.0.1  -->  http://127.0.0.1/
https://localhost  -->  https://localhost/
https://localhost?  -->  https://localhost/?
https://localhost/  -->  https://localhost/
https://my.site.com  -->  https://my.site.com/
https://my.site.com:443?  -->  https://my.site.com:443/?
https://my.site.com/  -->  https://my.site.com/
https://my.site.com/about.php  -->  https://my.site.com/about.php
https://my.site.com/about.php?  -->  https://my.site.com/about.php?
https://my.site.com/about  -->  https://my.site.com/about/
https://my.site.com/about?  -->  https://my.site.com/about/?
https://my.site.com/about/  -->  https://my.site.com/about/
https://my.site.com/about/?  -->  https://my.site.com/about/?
https://my.site.com/about?query  -->  https://my.site.com/about/?query
https://my.site.com/about/?query  -->  https://my.site.com/about/?query
https://my.site.com/about.php?query  -->  https://my.site.com/about.php?query
https://my.site.com/about#hash  -->  https://my.site.com/about/#hash
https://my.site.com/about/#hash  -->  https://my.site.com/about/#hash
https://my.site.com/about.php#hash  -->  https://my.site.com/about.php#hash
https://my.site.com/about?query#hash  -->  https://my.site.com/about/?query#hash
https://my.site.com/about/?query#hash  -->  https://my.site.com/about/?query#hash
https://my.site.com/folder.name/about?query  -->  https://my.site.com/folder.name/about/?query
https://my.site.com/about?query#hash:http://test.com?q  -->  https://my.site.com/about/?query#hash:http://test.com?q

Explaination (All)

• Level 1 - Lets just think about your examples:

^([^?#]+?)\/?([?#].*)?$

Group #1: ^ In first, [^?#] Any character except ?/#, Go much but lazy +? (Stop on first possible, by looking to next)
Ignore: \/? Then if a / exist or not
Group #2: [?#] = ?/# And .* Any much character next to that till $ End, (...)? If exist

It work well. But it will deal not right with:

https://my.site.com/about.php?query  -->  https://my.site.com/about.php/?query  !!!

So let's add an exception...

• Level 2 - How if we take possible file name Name.name.name.ext as Group #2?

^([^?#]+?)\/?((?:[^/?#]+\.[^/?#]+)?(?:[?#].*)?)$

(?:...) Non-Capturing group
([^/?#]+\.[^/?#]+)? Look for any possible file name or (?:[?#].*)? Any possible query or anchor strings

Now everything is OK, except this:

https://my.site.com?  -->  https://my.site.com?  !!!

So we need another exception in Group #1

• Level 3 - Take just domain URI as an alternative

^([^/]+:\/\/[^/#?]+|[^?#]+?)\/?((?:[^/?#]+\.[^/?#]+)?(?:[?#].*)?$)

(...|...) Alternative [^/]+:\/\/[^/#?]+ First check if (not lazy) any pattern like ...://... till not / # ? exist?

Now it work great!

---

+ Explaination (Considered)

• Level 4 - How if we just add a Not-Accepting . & / character set in first group to just match considered URIs and ignore others?

^([^/]+:\/\/[^/#?]+|[^?#]+\/[^/.?#]+)([?#].*)?$

\/[^/.?#]+ Check if after last / the set of characters be not /.?#

Now it is even smaller and faster!

---

Analyzing other method

As @károly-szabó answered well here, instead of looking for Not-Accepted character sets, we can look for matched pattern.
So if we want to use the method but in simpler way (2 Groups) (+ Some minor optimization), the regex will be:

^(https?:\/\/[\w.:-]+\/?(?:[\w.-]+\/)*[\w-]+(?!\/))([?#].*)?$

But URI path Accepted characters are more.

So a wider version of that Regex can be:

^(https?:\/\/[\w.:-]+\/?(?:[\w!#-)+-.;=@~]+\/)*[\w!#-);=@~+,-]+(?!\/))([?#].*)?$

Try it here: https://regexr.com/6elea

Note: Still "multibyte Unicode as domain name is allowed" but i ignored that in this method.

---

P.S.

Actually i don't think that we should rewrite it on IIS, because of these reasons:

• Anchors char # can be part of a folder name (by %23)
• A file name can have no extension
• IIS/Browsers usually will (/should) handle Anchors/Queries
  Ref:

  • IIS: UrlRewrite middleware query strings are preserved

  • Google/Anchor tags are stripped from URLs

  • RFC URI References

  • URI Wiki

  • How does IIS URL Rewrite handle # anchor tags

I Mean:

https://my.site.com/  -->  (=Call root)
https://my.site.com/about  -->  (=Call root > Folder/File name about) 
https://my.site.com/about/  -->  (=Call root > Folder name about) 
https://my.site.com/about?query  -->  (=Call root > Folder/File name about + Query)
https://my.site.com/about/?query  -->  (=Call root > Folder name about + Query)
https://my.site.com/about.php?query  -->  (=Call root > File name about.php + Query)
[When browser strip it:]
https://my.site.com/about#hash  -->  (=Call root > Folder/File name about + Anchor)
https://my.site.com/about/#hash  -->  (=Call root > Folder name about + Anchor)
https://my.site.com/about.php#hash  -->  (=Call root > File name about.php + Anchor)

[If not?]
https://my.site.com/folder#name/?query#hash
https://my.site.com/folder.name/about.php?query=one/two

Answer 2

You can try with this regex https://regex101.com/r/6TSqaP/2. This is matching every provided example and solves the problem if the url already has an ending '/'.

^((?:https?:\/\/[\w\.\-]*)(?:[\w\-]+\/)*(?:[\w\-]+)(?!\/))(\?.*?)?(\#.*?)?$

I used your second example as base for my regex, with the following logic. The parts of the url: scheme://authority/path?query#fragment

1. first capture group matches the scheme://authority/path part of the url
2. second capture group optional and matching the ?query
3. third capture group also optional and for the #fragment

regex explanation

^(                            # should start with this
    (?:https?:\/\/[\w\.\-]*)  # match the http or https protocol and the domain
    (?:[\w\-]+\/)*            # match the path except the last element of it (optional)
    (?:[\w\-]+)(?!\/)         # match the last path element, but only if it's not closed with '/'
)                             # {R:1}
(\?.*?)?                      # {R:2} query (optional)
(\#.*?)?                      # {R:3} fragment (optional)
$                             # string should end

Nginx

<rule name="AddTrailingSlash" stopProcessing="true">
  <match url="^((?:https?:\/\/[\w\.\-]*)(?:[\w\-]+\/)*(?:[\w\-]+)(?!\/))(\?.*?)?(\#.*?)?$" />
  <action type="Redirect" url="{R:1}/{R:2}{R:3}" redirectType="Permanent" />
</rule>

Edit: Updated regex to handle dashes (-) and multiple path elements