WordPress WebP Displays as Blank: CDN & Cache Misses Explained

Published On - September 12, 2025

Jonathan Dough Content

One of the most frustrating issues for WordPress website owners and developers is noticing that WebP images display as blank placeholders, especially after integrating performance optimization techniques like content delivery networks (CDNs) and caching mechanisms. While WebP is an efficient, modern image format supported by major browsers, its misbehavior in displaying correctly on a live site is usually not a fault of the format itself, but rather the misalignment between file delivery, caching, and browser compatibility.

This article delves into the reasons why WebP images sometimes appear blank when served via WordPress, especially when CDNs and cache systems are involved. It also provides best practices to troubleshoot and resolve this recurring issue.

The Rise of WebP in WordPress

WebP, developed by Google, is a next-gen image format that significantly reduces image sizes without losing visual quality. WordPress began supporting WebP natively starting from version 5.8, making it easier for site admins to upload and display WebP files just like any standard image format.

Benefits of WebP include:

  • Smaller file sizes compared to JPEG and PNG
  • Faster loading times for web pages
  • Responsive image handling across devices

However, many site owners soon realize that after enabling these formats, their images work perfectly on some devices or networks but appear blank on others. This discrepancy often leads developers to inspect deeper into the delivery pipeline.

Root Causes: Why WebP Images Display as Blank

The issue typically arises from one or more of the following:

  • Incompatible browser requests
  • CDN not delivering correct content types
  • Cache misses and outdated assets
  • Incorrect rewrite rules or server configurations

Let’s take a closer look at how CDNs and caching specifically contribute to this issue.

CDN Behavior and MIME Type Issues

CDNs like Cloudflare, KeyCDN, or StackPath cache content to deliver it closer to the end-user, reducing load time. However, they depend on proper content headers, especially the Content-Type header, to serve images correctly. For WebP, the browser expects a header of image/webp. If the CDN incorrectly classifies the WebP file—as application/octet-stream or omits the header entirely—browsers may not render the image and display blank placeholders instead.

Moreover, some older or misconfigured CDNs might not cache or serve WebP formats at all unless explicitly configured to do so.

Caching: When Old Rules Break New Content

Another culprit is server-side or plugin-based caching. WordPress caching plugins like W3 Total Cache or WP Rocket may incorrectly serve cached versions of pages that reference the wrong image URLs or are optimized for a different image format altogether. This can happen when:

  • A cached page attempts to display a WebP image to a browser that doesn’t support it
  • Cache rules have not been updated post WebP implementation
  • The CDN or edge server stores and serves stale assets

In essence, the cached version bypasses negotiation between client and server regarding image format compatibility, leading to blank images for unsupported browsers.

Diagnosing the Problem

There are a few steps to reliably identify the issue:

  1. Browser Test: Open the site in multiple browsers. If images show in Chrome but not in Safari or Firefox, it may be a format compatibility or cache issue.
  2. Inspect Headers: Check the Content-Type in the browser’s developer tools under the Network tab. For WebP, it should read image/webp.
  3. Bypass CDN and Cache: Temporarily disable CDN and cache plugins to isolate the issue. If images display correctly without these optimizations, they are the likely cause.
  4. Access Image Directly: Try accessing the WebP image URL directly. If it downloads or shows up correctly, problem lies within HTML reference or page delivery flow.

How to Fix the WebP Blank Display Issue

Once the root causes are identified, resolving the issue is a matter of reconfiguration and validation. Here are several proven methods:

1. Correct MIME Type in Server Headers

Ensure your server is configured to send Content-Type: image/webp for .webp files. This can be done via Apache’s .htaccess file or NGINX’s configuration:


AddType image/webp .webp

2. CDN Configuration Fixes

If using a CDN, make sure:

  • Edge servers are purged of old content
  • MIME types are correctly detected and passed through
  • CDN supports content negotiation for user agents

3. Smart Fallback For Non-Compatible Browsers

Use the <picture> HTML element to provide a WebP version first, with fallback to JPEG/PNG:


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

4. Clear and Rebuild Cache

Purge all caches—browser, WordPress plugin, and CDN. Rebuild the cache using updated configurations. Many issues resolve once new, correctly referenced assets are re-cached by CDNs and plugins.

5. Use a WebP-Compatible Plugin

Plugins like ShortPixel, EWWW Image Optimizer, and Imagify help convert and serve WebP images the right way. Most offer fallback logic and CDN integration options to ensure consistent delivery.

Best Practices for Using WebP in WordPress

  • Always use fallback formats via <picture> tags
  • Test after every cache/CDN change to avoid regressions
  • Use diagnostic tools like GTmetrix, WebPageTest, and browser dev tools
  • Integrate with image CDNs that offer WebP conversion (e.g., Imgix, Cloudinary)

Conclusion

The blank WebP image issue in WordPress can be perplexing, especially with multiple components—browser compatibility, caching, CDN delivery—in play. However, by systematically diagnosing and aligning your server headers, CDN setup, and caching layers, you can eliminate these rendering problems effectively. Keep in mind the end user’s experience and prioritize graceful fallback mechanisms to ensure compatibility across the board.

FAQ

Q: Why do my WebP images show as blank only in Firefox?
Firefox may interpret improperly served WebP files—especially with incorrect MIME types—as unsupported, resulting in blank displays. Verify the Content-Type header is set correctly to image/webp.
Q: Are older CDNs compatible with WebP images?
Not all CDNs handle WebP out of the box. Some require manual configuration to detect and serve WebP files correctly, while others do not cache them unless explicitly instructed to do so.
Q: How can I test WebP fallback behavior?
You can use browser extensions to change the User-Agent string or manually disable WebP support in developer tools. This helps test if your fallback JPEG or PNG is served correctly.
Q: Will clearing cache always fix WebP issues?
Not always, but it’s an essential step. Cached assets—either in CDN or plugin cache—can serve outdated or misconfigured content, which may be resolved after cache flushing.
Q: What plugin supports WebP with automatic fallback?
Plugins like ShortPixel and EWWW Image Optimizer offer automatic fallback to JPEG/PNG for unsupported browsers, ensuring consistent image rendering across platforms.