How to debug .htaccess RewriteRule not working - apache

Question

I have a RewriteRule in a .htaccess file that isn't doing anything. How do I troubleshoot this?
How can I verify if the .htaccess file is even being read and obeyed by Apache? Can I write an echo "it is working" message, if I do write it, where would that line be echoed out?
If the .htaccess file isn't being used, how can I make Apache use it?
If the .htaccess is being used but my RewriteRule still isn't having an effect, what more can I do to debug?

Answer 1

Enter some junk value into your .htaccess
e.g. foo bar, sakjnaskljdnas
any keyword not recognized by htaccess
and visit your URL. If it is working, you should get a
500 Internal Server Error
Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request....
I suggest you to put it soon after RewriteEngine on.
Since you are on your machine. I presume you have access to apache .conf file.
open the .conf file, and look for a line similar to:
LoadModule rewrite_module modules/mod_rewrite.so
If it is commented(#), uncomment and restart apache.
To log rewrite
RewriteEngine On
RewriteLog "/path/to/rewrite.log"
RewriteLogLevel 9
Put the above 3 lines in your virtualhost. restart the httpd.
RewriteLogLevel 9 Using a high value for Level will slow down your Apache server dramatically! Use the rewriting logfile at a Level greater than 2 only for debugging!
Level 9 will log almost every rewritelog detail.
UPDATE
Things have changed in Apache 2.4:
FROM Upgrading to 2.4 from 2.2
The RewriteLog and RewriteLogLevel directives have been removed. This functionality is now provided by configuring the appropriate level of logging for the mod_rewrite module using the LogLevel directive. See also the mod_rewrite logging section.
For more on LogLevel, refer LogLevel Directive
you can accomplish
RewriteLog "/path/to/rewrite.log"
in this manner now
LogLevel debug rewrite_module:debug

Answer 2

The 'Enter some junk value' answer didn't do the trick for me, my site was continuing to load despite the entered junk.
Instead I added the following line to the top of the .htaccess file:
deny from all
This will quickly let you know if .htaccess is being picked up or not. If the .htaccess is being used, the files in that folder won't load at all.

Answer 3

Generally any change in the .htaccess should have visible effects. If no effect, check your configuration apache files, something like:
<Directory ..>
...
AllowOverride None
...
</Directory>
Should be changed to
AllowOverride All
And you'll be able to change directives in .htaccess files.

Answer 4

To answer the first question of the three asked, a simple way to see if the .htaccess file is working or not is to trigger a custom error at the top of the .htaccess file:
ErrorDocument 200 "Hello. This is your .htaccess file talking."
RewriteRule ^ - [L,R=200]
On to your second question, if the .htaccess file is not being read it is possible that the server's main Apache configuration has AllowOverride set to None. Apache's documentation has troubleshooting tips for that and other cases that may be preventing the .htaccess from taking effect.
Finally, to answer your third question, if you need to debug specific variables you are referencing in your rewrite rule or are using an expression that you want to evaluate independently of the rule you can do the following:
Output the variable you are referencing to make sure it has the value you are expecting:
ErrorDocument 200 "Request: %{THE_REQUEST} Referrer: %{HTTP_REFERER} Host: %{HTTP_HOST}"
RewriteRule ^ - [L,R=200]
Test the expression independently by putting it in an <If> Directive. This allows you to make sure your expression is written properly or matching when you expect it to:
<If "%{REQUEST_URI} =~ /word$/">
ErrorDocument 200 "Your expression is priceless!"
RewriteRule ^ - [L,R=200]
</If>
Happy .htaccess debugging!

Answer 5

Perhaps a more logical method would be to create a file (e.g. test.html), add some content and then try to set it as the index page:
DirectoryIndex test.html
For the most part, the .htaccess rule will override the Apache configuration where working at the directory/file level

Answer 6

If you have access to apache bin directory you can use,
httpd -M to check loaded modules first.
info_module (shared)
isapi_module (shared)
log_config_module (shared)
cache_disk_module (shared)
mime_module (shared)
negotiation_module (shared)
proxy_module (shared)
proxy_ajp_module (shared)
rewrite_module (shared)
setenvif_module (shared)
socache_shmcb_module (shared)
ssl_module (shared)
status_module (shared)
version_module (shared)
php5_module (shared)
After that simple directives like Options -Indexes or deny from all will solidify that .htaccess are working correctly.

Answer 7

To test your htaccess rewrite rules, simply fill in the url that you're applying the rules to, place the contents of your htaccess on the larger input area and press "Test" button.
http://htaccess.mwl.be/

Answer 8

Check whether the permission to read and execute the .htaccess by apache process is possible. Looking into the error_log of Apache will help you to sort the permission related error.

Answer 9

Why not put some junk in your .htaccess file and try to reload apache. If apache fails to start you know its working. Remove the junk then reload apache if it loads congrats you configured .htaccess correctly.