Redirect 301 in htaccess Codeigniter

How to do 301 redirects in CI? I am creating a new website in CI and I would like to do 301 redirects from the earlier version of the website, where the URL structure looks a bit different, so I wanted to redirect the most important subpages in htaccess, but the regular rules in htaccess do not work for me, I think because of entries in routes.php

$route['(:any)/(:any)/(:num)'] = 'ads/cat/$1/$2/$3';
$route['(:any)/(:any)'] = 'ads/cat/$1/$2';
$route['(:any)'] = 'ads/cat/$1';

and my htaccess file

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?/$1 [L]

and I would like to redirect for example

RewriteRule ^oldcat1/oldcat2/oldcat3/ http://localhost/newcat1/newcat2 [R=301,L]

But this redirect doesnt work. How to deal with this?

Answer

You need to make sure you place your external redirects before the existing directives that send the request to your CodeIgniter front-controller, otherwise, they simply won’t be processed.

For example:

# External redirects
RewriteRule ^oldcat1/oldcat2/oldcat3/ http://localhost/newcat1/newcat2 [R=301,L]

# Front-controller
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?/$1 [L]

This doesn’t have anything to do with routes you might have defined in CodeIgniter since .htaccess is processed before routes.php is called.