Apache's mod_rewrite provides a powerful method for manipulating URLs on the server side, converting them into clean and user-friendly formats. This guide walks you through understanding mod_rewrite, its benefits, and how to configure it on a VPS running Apache.

Background

When a URL is entered, it undergoes scrutiny against a set of predefined rules. These rules identify specific patterns or keywords within the URL. If a designated keyword is detected and the rule aligns, it triggers the replacement of the identified portion with a predetermined string – thereby generating a new URL.

mod_rewrite proves invaluable as it empowers users to transform URLs into clean and user-friendly formats. This is particularly advantageous for end-users without technical expertise, as the simplified URLs are easily comprehensible and search engine-friendly.

To illustrate the concept of a clean URL, consider these examples:

  1. URL1: http://modrewriteexample.com/client.php?id=A786#234QA
  2. URL2: http://modrewriteexample.com/client/=A786#234QA/
  3. URL3: http://modrewriteexample.com/client/Martha/

Among these three URLs, the third one stands out as significantly more readable and comprehensible to the end user. URL 3 qualifies as a clean URL in this context.

Prerequisites

Before proceeding, ensure SSH access to your VPS.

How to Set Up mod_rewrite

  1. Step 1: Install Apache

    For this demonstration on Ubuntu 18.04, use the built-in package installer, apt-get. Begin by updating it:

    sudo apt-get update

    Then proceed with the installation of Apache2:

    sudo apt-get install apache2

  2. Step 2: Enable mod_rewrite

    Enable mod_rewrite with the following command:

    sudo a2enmod rewrite

    This command activates the rewrite mode, or informs you if it's already in use. Subsequently, restart Apache:

    sudo service apache2 restart

  3. Step 3: Create the .htaccess File

    To establish pre-defined URL rewrite rules, utilize the .htaccess file. Users can manually write rules in this file. Since the server references this file, any errors could result in a server error. The .htaccess file should be created at the root for testing the rewrite functionality.

    Start by running the following command:

    sudo nano /var/www/html/.htaccess

    This command either creates the .htaccess file if absent or opens it if it already exists. Save and exit in nano by pressing CTRL+O to save and CTRL+X to exit.

    Next, open the 000-default.conf file located in the /etc/apache2/sites-enabled/ directory:

    sudo nano /etc/apache2/sites-enabled/000-default.conf

    Within this file, insert the following block after the string:

    
    Options Indexes FollowSymLinks MultiViews
    AllowOverride All
    Order allow,deny
    allow from all

    Save the file similar to the .htaccess. Restart Apache, as mentioned in step two, for the changes to take effect.

  4. Step 4: Create a URL Rewrite Rule

    URL rewriting involves selecting a clean URL and transforming it into actual paths that lead to code. It comprises the following components:

    • A pre-defined rewrite rule
    • A pattern serving as a matching reference with the entered URL
    • Rewriting lines specifying the path to be called by the server at that point

    Let's create a rewrite rule to redirect a user to the About_us.html page if the requested URL is http://ip/Aboutus. For successful execution, ensure the rewrite engine is activated. Open the .htaccess file and add the following syntax:

    RewriteEngine on
RewriteRule ^About_us$ About_us.html [NC]

    Breaking down the syntax:

    • About_us is the pattern redirected to About_us.html upon matching
    • NC is a flag for case insensitivity
    • ^ indicates matching immediately after the IP address

    Congratulations! You have successfully created a mod_rewrite rule!

Conclusion

Easy, clean, and user-friendly URLs are crucial for a successful website. Incorporating keywords into URLs is essential for memorability and SEO. With mod_rewrite, you can create numerous rewrite rules to enhance your website's URL structure.