Tutorial on how to redirect and rewrite URLs using Apache modules

Easy to remember

It will make URLs easier to remember. For example, you may have a URL

http://exampleserver.com/view/index.php?user=bob

It is possible to rewrite it as

http://exampleserver.com/~bob

This will enable the user Bob to give out his URL to people and place it on his business cards.

Search Engine Optmization

Some search engines dislike URLs with GET arguments placed in the URL. e.g. you may have the URL

http://exampleserver.com/article.php?type=apache&article_id=231

Some search engines may skip over this, but if we rewrite the URL to

http://exampleserver.com/articles/apache/231

then it it is more likely to be indexed by the search engines.

Document redirection

Inevitably, when you haven't organised your URLs correctly and you need to restructure, redirecting users from the old URL to the new page is desirable. Apache can do this for you, so you don't even need to use the refresh meta tag for this.

It is better to give the browser an redirect error message, instead of having the meta tags do the redirection.

Example hiding a parameter to make it look like user home dirs

The example below translates the original URL

http://exampleserver.com/user/view.php?name=peter

to

http://exampleserver.com/~peter

This will allow the php script to run with the argument name equal to the given username.

The .htaccess contains the following:

RewriteEngine on
RewriteRule ^~(.*)    user/view.php?name=$1

You need to have some experience in using regular expressions to make sense of this, but hopefully the example was enough to get you started.

The ^ character is an anchor saying from the start of the line.

~ is literally the ~ we are trying to match in the URL.

(.*) is broken up into three pieces.

1. .

   This means any character.

2. *

   This follows the . character, and means any number of them.

3. ()

   This means count as part of a match, so we can refer to it using $1 for the first match.

Moving directories

I recently moved all our struts pages from the tomcat section to the JSP section. To preserve existing links to our site, I added the following rule

RewriteRule kb/app/tomcat/struts/(.*) /kb/prg/java/jsp/struts/$1 [R]

The second argument contains a leading /, because the files local path on the server was being added to the URL.

Domain Name prefix

You can redirect traffic for example.com to www.example.com

RewriteEngine On
RewriteCond %{HTTP_HOST} !^(.*)\.example\.com\ [NC]
RewriteRule ^(.*)$ http://www.example.com/$1 [R=301,L]
      

The RewriteCond above ignores requests that already contain a subdomain.

Alternatively, you can redirect all www.* traffic to your normal domain.

RewriteEngine On
RewriteCond %{HTTP_HOST} ^www\.example\.com$ [NC]
RewriteRule ^(.*)$ http://example.com/$1 [R=301,L]
      

To redirect any host that doesn't match, you could use something like

RewriteEngine On
RewriteCond %{HTTP_HOST} !^example\.com [NC]
RewriteRule ^(.*)$ http://example.com/$1 [R=301,L]
      

This helps to get rid of the numeric IP being used as the host name.

Moving Domain

You can also redirect traffic between domains

RewriteEngine On
RewriteRule old/pages/(.*) http://example.com/archive/$1 [R=301]
      

You can specify a new domain as part of the redirection.

301 means that it has been moved permanently.

If you use [R] instead of [R=301], then it defaults to sending a 302, which is moved temporarily.

Redirecting scheme from https to http

Add the following to your .htaccess

# turn on mod_rewrite
RewriteEngine On

# check that it is https
RewriteCond %{HTTPS} =on
# redirect to the plain http site
RewriteRule ^(.*)$ http://magicmonster.com/$1 [R=301,L]

Instead if .htaccess you can also add this into the module conf file.

mod_rewrit

If you have mod_rewrit instead, it isn't a typo, but an incomplete and undocumented version of mod_rewrite that is was meant to be more secure. Don't even bother trying to get support for this.

Troubleshooting

RewriteLog /usr/local/apache/logs/mod_rewrite.log
RewriteLogLevel 9

http://dev/~aelst/fish.html

http://dev/~aelst/whale.html

RewriteEngine on
RewriteRule fish\.html whale.html

Not Found
The requested URL /home/aelst/public_html/whale.html was not found on this server.

http://dev/~aelst/whale.html

RewriteEngine on
RewriteRule fish\.html /~aelst/whale.html

RewriteEngine on
RewriteBase /~aelst/
RewriteRule fish\.html whale.html