How to Minify CSS and JavaScript Files in WordPress (Step-by-Step Guide)

According to Google research, site performance impacts core web vitals which directly correlates with higher search rankings and revenue.

Minifying CSS and JavaScript files is an easy way to significantly improve site speed and performance.

Why You Should Minify Resources in WordPress

Minification removes whitespace, comments and unnecessary characters from code without affecting functionality.

Benefits include:

• Faster page load times: Removing extra bytes can reduce file sizes by up to 80%
• Better Core Web Vitals scores: Minification helps meet recommended CLS and FID thresholds
• Improved user experience: Lightweight resources lead to faster rendering and interactivity
• Higher search rankings: Google uses page experience signals as a ranking factor
• Increased revenue: Shoppers tend to abandon slow loading sites costing sales

This table demonstrates typical file size savings from minification:

Now let‘s see how to minify resources in WordPress.

Method 1: Using WP Rocket (Recommended)

WP Rocket is the most popular WordPress performance plugin with over 1 million active installs.

To enable minification with WP Rocket:

1. Install and activate the WP Rocket plugin
2. In the WordPress dashboard, go to Settings → File Optimization
3. Under the CSS Files section, check the Minify CSS files option
4. Click Activate Minify CSS and dismiss the warning popup
5. Scroll down to the JavaScript Files section
6. Check the Minify JavaScript files option
7. Click Activate Minify JavaScript
8. Click Save Changes and clear cache

These simple steps will minify CSS and JavaScript files served to visitors.

According to GTmetrix tests, WP Rocket minification can improve page speeds by over 50% along with significant reductions in TTFB and requests.

Method 2: Using the Autoptimize Plugin

Autoptimize is a lightweight all-in-one performance plugin with over 1 million installs.

To minify resources using Autoptimize:

1. Install and activate Autoptimize
2. In your WordPress dashboard, go to Settings → Autoptimize
3. Under the JavaScript Options section, check Optimize JavaScript Code
4. Scroll down to the CSS Options sections
5. Check the Optimize CSS Code option
6. Click Save Changes and then Empty Cache

Autoptimize will automatically minify CSS and JavaScript files served to visitors.

Based on tests, turning on these options can reduce CSS/JS sizes by over 70% leading to faster load times.

Method 3: Using SiteGround Optimizer (SiteGround Hosting)

SiteGround users can enable minification using the SG Optimizer plugin specially designed for their hosting environment.

To minify resources with SG Optimizer:

1. Ensure the SiteGround Optimizer plugin is installed and activated
2. Go to SG Optimizer → Frontend Optimization in your dashboard
3. Under CSS Frontend, turn on the Minify CSS files setting
4. Switch to the JavaScript tab
5. Turn on the Minify JavaScript files setting
6. Click Save Changes and clear caches

Minification will now be enabled for CSS and JavaScript files.

Based on data from SiteGround, the optimizer plugin can reduce file sizes by up to 82% with the minification feature.

Hopefully this guide helped you learn how to optimize resources in WordPress for faster load times using minification. Let me know if you have any other questions!