Every Apache administrator knows the pain of debugging RewriteRule and RewriteCond statements. The trial-and-error process of editing .htaccess files, uploading them to the server, and testing URLs can be incredibly time-consuming.

# Typical debugging cycle example
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)$ index.php?path=$1 [QSA,L]

Several online tools can help validate your rewrite rules before deploying them:

• htaccess.madewithlove.com - Provides real-time feedback with URL testing
• modrewritecheatsheet.com - Offers both testing and cheat sheet reference
• regex101.com - Useful for testing the regex patterns independently

The best testing tools should include:

1. Live preview of rule matching
2. Step-by-step rule processing visualization
3. Environment variable simulation
4. HTTP header testing capability
5. Redirect chain analysis

Let's test a common URL rewriting scenario:

# Test case: Convert /products/123 to product.php?id=123
RewriteEngine On
RewriteRule ^products/([0-9]+)$ product.php?id=$1 [NC,L]

# Test URLs:
/products/123     # Should match
/products/abc     # Should not match
/products/123/    # Might match depending on configuration

When online tools aren't enough, add logging to your server configuration:

# Enable rewrite logging (add to httpd.conf)
RewriteLog "/var/log/apache2/rewrite.log"
RewriteLogLevel 3

Remember to disable logging after debugging as it impacts performance.

• Forgetting the RewriteEngine On directive
• Incorrect regular expression escaping
• Missing [L] flag when needed
• Not considering the order of rules

Every Apache administrator knows the frustration of writing mod_rewrite rules that don't work as expected. You make changes, restart Apache, test in browser, repeat. This trial-and-error approach wastes hours. What we need is an immediate feedback loop.

Here are the best tools I've found for real-time mod_rewrite testing:

1. htaccess Tester (htaccess.madewithlove.com)

The most reliable online tester I've used. Example test case:

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^blog/([0-9]+)/?$ show_article.php?id=$1 [NC,L]

2. mod_rewrite Rule Tester (martinmelin.se/rewrite-rule-tester)

Great for complex rules with multiple conditions:

RewriteCond %{HTTP_HOST} ^example\.com$ [NC]
RewriteCond %{REQUEST_URI} !^/static/
RewriteRule (.*) http://www.example.com/$1 [R=301,L]

These tools handle advanced cases like:

• Chained RewriteRules with [S] flag
• Environment variables (%{ENV:})
• Server variables (%{HTTP_*})
• Query string preservation (QSA)

Online testers help identify these frequent issues:

# Missing leading slash
RewriteRule ^article/(.*)$ /articles/$1 [L]  # Correct
RewriteRule ^article/(.*)$ articles/$1 [L]   # Wrong

# Incorrect regex escaping
RewriteCond %{HTTP_HOST} example\.com$       # Correct
RewriteCond %{HTTP_HOST} example.com$        # Wrong

For server-specific testing, enable logging:

RewriteLog "/var/log/apache/rewrite.log"
RewriteLogLevel 3

Remember to disable this in production!