How to Convert WordPress Images to WebP (And Why You Should)

WebP images are 25-35% smaller than JPEG and PNG while maintaining the same visual quality. If you're not using WebP on your WordPress site in 2025, you're wasting bandwidth and hurting your search rankings.

What is WebP?

WebP is a modern image format developed by Google that provides superior compression compared to traditional formats. It supports both lossy and lossless compression, plus transparency (like PNG).

Why Convert to WebP?

1. Faster Page Load Times

Smaller images = faster loading. Slow images can destroy your site's performance. Google's data shows that as page load time increases from 1s to 3s, bounce rate increases by 32%.

• Users see content faster
• Less bandwidth consumed (crucial for mobile users)
• Lower hosting costs (less data transfer)

2. Better SEO Rankings

Google uses Core Web Vitals as ranking factors for image SEO. WebP directly improves Largest Contentful Paint (LCP), one of the key metrics.

3. Improved Mobile Experience

Over 60% of web traffic is mobile. WebP images load faster on slower connections and consume less mobile data.

4. Excellent Browser Support

As of 2025, WebP is supported by:

• Chrome/Edge: 95%+ (since 2010)
• Firefox: 93%+ (since 2019)
• Safari: 97%+ (since 2020)
• Mobile browsers: 96%+ coverage

For the ~3% of users on older browsers, you'll serve fallback JPEG/PNG images automatically (we'll cover this below).

How to Convert WordPress Images to WebP

There are three main approaches. Choose based on your technical comfort level and site size.

Method 1: Using a Plugin (Recommended)

Image optimization plugins handle everything automatically: conversion, fallbacks, and serving the right format to each user.

Using Altomatic Plugin

Step 1: Install and Activate

Go to Plugins → Add New, search for "Altomatic", install and activate.

Step 2: Configure Settings

Navigate to Settings → Altomatic:

• Enter your API key (sign up at altomatic.ai for 50 free credits/month)
• Enable "Convert to WebP" option
• Optionally enable AVIF for even better compression
• Choose whether to keep original images as fallbacks

Step 3: Convert Existing Images

Go to Media → Bulk Optimization:

• Select "Convert to WebP" option
• Choose whether to process all images or just specific ones
• Click "Start Bulk Optimization"
• Monitor progress - processing continues in background

Step 4: Automatic Future Conversions

Enable "Auto-optimize on upload" in settings. New images will automatically convert to WebP when you upload them.

Method 2: Using .htaccess Rules (Advanced)

If you have WebP versions of your images on the server, you can use .htaccess to serve them automatically.

<IfModule mod_rewrite.c>
  RewriteEngine On
  RewriteCond %{HTTP_ACCEPT} image/webp
  RewriteCond %{REQUEST_FILENAME}.webp -f
  RewriteRule ^(.*).(jpe?g|png)$ $1.$2.webp [T=image/webp,E=accept:1,L]
</IfModule>

<IfModule mod_headers.c>
  Header append Vary Accept env=REDIRECT_accept
</IfModule>

Method 3: Using <picture> Tags (Manual)

You can manually specify WebP sources with fallbacks using HTML picture elements:

<picture>
  <source srcset="image.webp" type="image/webp">
  <source srcset="image.jpg" type="image/jpeg">
  <img src="image.jpg" alt="Description">
</picture>

This gives you maximum control but requires manually editing every image. Not practical for WordPress sites with hundreds of images.

Do You Need to Keep Original Images?

Short answer: Yes, for fallback support.

Most WordPress WebP plugins work by:

1. Creating WebP versions alongside original JPEG/PNG files
2. Detecting browser support automatically
3. Serving WebP to compatible browsers
4. Serving original format to older browsers

This dual-format approach ensures compatibility while maximizing performance for 97% of users.

What About AVIF?

AVIF is even newer than WebP and offers 20% better compression. Browser support is now at 90%+ (as of 2025).

Altomatic and other modern plugins can generate all three formats automatically, serving the best option to each visitor.

Testing Your WebP Implementation

1. Check Image Format in Browser

• Right-click an image on your site
• Select "Inspect" or "Inspect Element"
• Look at the Network tab
• You should see images loading as .webp

2. Use Google PageSpeed Insights

Run your site through PageSpeed Insights. If WebP is working correctly, you should no longer see "Serve images in next-gen formats" warning.

3. Test Fallback Support

To verify fallbacks work:

• Use a browser that doesn't support WebP (like Internet Explorer)
• Or use browser DevTools to disable WebP support
• Images should still load (as JPEG/PNG)

Common Issues and Solutions

AddType image/webp .webp

Next Steps

1. Test your current setup

   Run PageSpeed Insights to see if you're already serving WebP

2. Choose a conversion method

   Plugin method is easiest for most WordPress users

3. Convert existing images

   Start with your most-visited pages, then bulk process the rest

4. Enable automatic conversion

   Set up auto-optimization for future uploads

5. Monitor performance improvements

   Track page load times and Core Web Vitals scores