How to redirect / convert any URL to lowercase?

Question

I am using:

<IfModule mod_rewrite.c>
    Options +FollowSymLinks
    RewriteEngine On   
    RewriteCond %{HTTP_HOST} ^example\.com [NC]
    RewriteRule (.*) http://example.com/$1 [L,R=301]
</IfModule>

But I want to rewrite all UPPERCASE characters to lowercase characters, e.g:

• OLD: /myfolder-sample-URL.html
• NEW: /myfolder-sample-url.html

Solution 1

To implement such redirect using mod_rewrite and .htaccess you need to use RewriteMap directive which cannot be placed in .htaccess -- only in server config / VirtualHost context. If you have such access:

1. Place this line inside <VirtualHost> block for your site:

RewriteMap lc int:tolower

2. Place this in your .htaccess:

RewriteCond %{REQUEST_URI} [A-Z]
RewriteRule . ${lc:%{REQUEST_URI}} [R=301,L]

This will redirect (301 Permanent Redirect) any URL that has at least 1 capital letter (Latin letters only) in path part of URL (query string is ignored) to the same but in lower case.

For example:

http://mydomain.com/myfolder-sample-URL.html
=> 
http://mydomain.com/myfolder-sample-url.html

http://mydomain.com/myfolder-sample-url.HTML
=> 
http://mydomain.com/myfolder-sample-url.html

but will do nothing for these URLs:

http://mydomain.com/myfolder-sample-url.html?say=MEOW
http://MYDOMAIN.com/myfolder-sample-url.html

If you want to restrict it to .html files only:

RewriteCond %{REQUEST_URI} [A-Z]
RewriteRule ^.+\.html$ ${lc:%{REQUEST_URI}} [NC,R=301,L]

---

Where to place: I would place it after domain name redirect rule:

RewriteEngine On

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

RewriteCond %{REQUEST_URI} [A-Z]
RewriteRule . ${lc:%{REQUEST_URI}} [R=301,L]

# your other rules

---

I also recommend using rel="canonical" links:

<link rel="canonical" href="PROPER_URL_HERE" />

• http://www.google.com/support/webmasters/bin/answer.py?answer=139394
• http://googlewebmastercentral.blogspot.com/2009/02/specify-your-canonical.html

---

If you do not need redirect, but rather ability to serve the file regardless of the file name case (case insensitive file names), then you can use mod_spelling ( http://httpd.apache.org/docs/current/mod/mod_speling.html ) and CheckCaseOnly On directive.

Solution 2

On Apache 2.4 you can convert the URL-path to lowercase in .htaccess (only) with an Apache Expression in a RewriteCond (mod_rewrite) directive. No need to define a RewriteMap in the server config (or write a plethora of rules to replace each letter one by one).

For example:

RewriteEngine On

RewriteCond expr "tolower(%{REQUEST_URI}) =~ /(.*)/"
RewriteRule [A-Z] %1 [R=301,L]

The RewriteRule pattern [A-Z] simply checks that there is at least one uppercase letter in the URL-path before continuing.

By passing expr as the TestString (1st arg) to the RewriteCond directive, the CondPattern (2nd arg) is treated as an Apache Expression. This performs a regex comparison which is always successful and the result of the tolower() function is captured by the parenthesised subpattern in the regex. This is then accessible using the %1 backreference in the RewriteRule substitution.

Note that this particular example just converts the URL-path. The query string (and hostname) remain unchanged.

The above checks every requested URL. To exclude all URLs that look like a static resource (ie. that end with what looks-like a file extension) then add a preceding condition with a negated expression. For example:

RewriteCond %{REQUEST_URI} !\.\w{2,4}$
RewriteCond expr "tolower(%{REQUEST_URI}) =~ /(.*)/"
RewriteRule [A-Z] %1 [R=301,L]

The \w shorthand character class already includes both upper and lowercase letters, so no need for the NC flag here.

To specifically target just .html files (as mentioned in the question) then use a case-insensitive condition that checks for this. For example:

RewriteCond %{REQUEST_URI} \.html$ [NC]
RewriteCond expr "tolower(%{REQUEST_URI}) =~ /(.*)/"
RewriteRule [A-Z] %1 [R=301,L]

NB: Test first with a 302 (temporary) redirect before committing to a 301 (permanent) redirect so as to avoid potential caching issues.

Solution 3

Add this to the top of your .htaccess

SOURCE: Htaccess to Redirect Uppercase to Lowercase

RewriteEngine On
RewriteBase /

# If there are caps, set HASCAPS to true and skip next rule
RewriteRule [A-Z] - [E=HASCAPS:TRUE,S=1]

# Skip this entire section if no uppercase letters in requested URL
RewriteRule ![A-Z] - [S=28]

# Replace single occurance of CAP with cap, then process next Rule.
RewriteRule ^([^A]*)A(.*)$ $1a$2
RewriteRule ^([^B]*)B(.*)$ $1b$2
RewriteRule ^([^C]*)C(.*)$ $1c$2
RewriteRule ^([^D]*)D(.*)$ $1d$2
RewriteRule ^([^E]*)E(.*)$ $1e$2
RewriteRule ^([^F]*)F(.*)$ $1f$2
RewriteRule ^([^G]*)G(.*)$ $1g$2
RewriteRule ^([^H]*)H(.*)$ $1h$2
RewriteRule ^([^I]*)I(.*)$ $1i$2
RewriteRule ^([^J]*)J(.*)$ $1j$2
RewriteRule ^([^K]*)K(.*)$ $1k$2
RewriteRule ^([^L]*)L(.*)$ $1l$2
RewriteRule ^([^M]*)M(.*)$ $1m$2
RewriteRule ^([^N]*)N(.*)$ $1n$2
RewriteRule ^([^O]*)O(.*)$ $1o$2
RewriteRule ^([^P]*)P(.*)$ $1p$2
RewriteRule ^([^Q]*)Q(.*)$ $1q$2
RewriteRule ^([^R]*)R(.*)$ $1r$2
RewriteRule ^([^S]*)S(.*)$ $1s$2
RewriteRule ^([^T]*)T(.*)$ $1t$2
RewriteRule ^([^U]*)U(.*)$ $1u$2
RewriteRule ^([^V]*)V(.*)$ $1v$2
RewriteRule ^([^W]*)W(.*)$ $1w$2
RewriteRule ^([^X]*)X(.*)$ $1x$2
RewriteRule ^([^Y]*)Y(.*)$ $1y$2
RewriteRule ^([^Z]*)Z(.*)$ $1z$2

# If there are any uppercase letters, restart at very first RewriteRule in file.
RewriteRule [A-Z] - [N]

RewriteCond %{ENV:HASCAPS} TRUE
RewriteRule ^/?(.*) /$1 [R=301,L]

Alternatively your host may support mod_speling, in which if they do, you can use in the server config, virtual host, directory or within a .htaccess file, example below:

<IfModule mod_speling.c>
    CheckCaseOnly On
    CheckSpelling On
</IfModule>

Comments

[LazyOne]

To implement such redirect using mod_rewrite and .htaccess you need to use RewriteMap directive which cannot be placed in .htaccess -- only in server config / VirtualHost context. Do you have access to server config? Can you change it? If no -- then you can only implement it when executing the actual page (using PHP/ASP.NET etc).

[CarrKnight]

Thanks for suggestion, Yes I have access to RewriteMap, so... what should I do now?

[Stephen Ostermiller]

Is there any reason to prefer to use these 26 separate rewrite rules opposed to the two line rewrite ruling using lc: from LazyOne's answer?

[Simon Hayter]

Depends on the situation, the one I listed requires just on htaccess however the shorter version requires both virtual host and htaccess because of the initial RewriteMap lc int:tolower requirement.

[Simon Hayter]

The reason I posted this answer was because I closed a very similar question which asked for a htaccess only method.

[MrWhite]

"If you do not need redirect, ... you can use mod_spelling" - mod_speling (one L) will, in fact, issue a 301 redirect to the intended document.