301 redirect in .htaccess from uppercase to lowercase characters

In web development, managing URL consistency is crucial for SEO and user experience. One common task is redirecting URLs with uppercase characters to their lowercase counterparts. This article provides a working example for redirecting URLs like http://domain.com/sUcH_liNKs to their lowercase versions using .htaccess. While the solution is large and not very elegant, it effectively performs the desired redirects.

Implementing the Redirect

To redirect URLs from uppercase to lowercase using .htaccess, follow these steps:

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 occurrence 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]

Explanation of the .htaccess Rules

Here’s a breakdown of the .htaccess rules used in the solution:

• RewriteEngine On: Enables the runtime rewriting engine.
• RewriteBase /: Sets the base URL for all subsequent relative URLs.
• RewriteRule [A-Z] – [E=HASCAPS:TRUE,S=1]: Checks if the URL contains any uppercase letters. If it does, it sets the environment variable HASCAPS to true and skips the next rule.
• RewriteRule ![A-Z] – [S=28]: Skips the entire section if there are no uppercase letters in the requested URL.
• RewriteRule ^([^A]*)A(.*)$ $1a$2: Replaces a single occurrence of the uppercase letter ‘A’ with the lowercase letter ‘a’ and processes the next rule.
• RewriteRule [A-Z] – [N]: Restarts the rewrite process if any uppercase letters are found.
• RewriteCond %{ENV:HASCAPS} TRUE: Checks if the HASCAPS environment variable is set to true.
• RewriteRule ^/?(.*) /$1 [R=301,L]: Redirects the URL to its lowercase version with a 301 permanent redirect.

Conclusion

Redirecting URLs from uppercase to lowercase is important for maintaining consistent URLs, which is beneficial for SEO and user experience. The .htaccess solution provided in this article ensures that all incoming requests with uppercase letters are redirected to their lowercase counterparts. While the solution may seem large and complex, it is effective and ensures that your URLs remain consistent.