Redirecting using rewrite rules from international top level domains to a language subdirectory doesn't change the domain name

Redirecting using rewrite rules from international top level domains to a language subdirectory doesn't change the domain name - .htaccess files are extremely useful in many cases for users who either do not have root permissions or for users who simply aren't comfortable in making changes in their web server's configuration file. Trying to debug .htaccess not working isn't always the easiest thing to do, however, hopefully by checking the discuss below mentioned about htaccess, redirects, apache, mod-rewrite, .htaccess common problems as well as the troubleshooting tips, you'll have a better grasp on what you may have to modify to get your .htaccess file running smoothly.Problem :

I want to change from TLDs to TLD and language code.
Right now we have 4 TLDs for our webpage:

example.de
example.com
example.nl
example.fr

Now I want to change our settings of our CMS (Contao) to have only one TDL and language short terms:

example.com/de/
example.com/en/
example.com/nl/
example.com/fr/

Now if you type example.com, Contao detects the browser language and redirects to the right language short term.

Is this the right way to redirect:

RewriteCond %HTTP_HOST example.de$ [NC]
RewriteRule ^((?![a-z]2/).*)$ /de/$1 [R=301,L]

RewriteCond %HTTP_HOST example.com$ [NC]
RewriteRule ^((?![a-z]2/).*)$ /en/$1 [R=301,L]

RewriteCond %HTTP_HOST example.nl$ [NC]
RewriteRule ^((?![a-z]2/).*)$ /nl/$1 [R=301,L]

RewriteCond %HTTP_HOST example.fr$ [NC]
RewriteRule ^((?![a-z]2/).*)$ /fr/$1 [R=301,L]

Now I get redirected to example.de/de/app.php all the time.

Solution :

You didn't specify the domain name in the rewrite rule destination, so it is using the current one. You should add example.com to the rewrite rule to change the domain:

RewriteCond %HTTP_HOST example.de$ [NC]
RewriteRule ^((?![a-z]2/).*)$ http://example.com/de/$1 [R=301,L]

You shouldn't need the ^(?![a-z]2/) in that rule for the country code domains. That is checking and only redirecting if there isn't a two letter subdirectory already on the URL. For that domain, there shouldn't be one anyway. So you can probably use a simpler rule:

RewriteCond %HTTP_HOST example.de$ [NC]
RewriteRule ^(.*)$ http://example.com/de/$1 [R=301,L]

You can make all your country code domains into a single rule and then use a separate special rule for .com. The .com rule will need your check that the country code doesn't already exist.

RewriteCond %HTTP_HOST example.([a-z]2)$ [NC]
RewriteRule ^(.*)$ http://example.com/%1/$1 [R=301,L]

RewriteCond %HTTP_HOST example.com$ [NC]
RewriteRule ^((?![a-z]2/).*)$ /en/$1 [R=301,L]

With those two rules you should be all set. When you are testing, be sure to clear your browser cache each time you test. Otherwise, previous incorrect redirects could get cached and give you redirect loops.

Additionally, if you would like to do some further testing, give the htaccess tester tool a try. It allows you to specify a certain URL as well as the rules you would like to include and then shows which rules were tested, which ones met the criteria, and which ones were executed.