How to Fix WordPress Media Upload Issues After Installing a Cache / Compression Plugin — File Permission & Memory Limit Fixes That Helped Users

After installing a caching or compression plugin on your WordPress site, it’s not uncommon to run into unexpected problems—especially with uploading new media files. Suddenly, that seemingly unrelated action of optimizing site performance begins to interfere with your ability to update content. This issue can often be traced back to changes in file permissions, memory limits, or plugin compatibility quirks.

TLDR (Too long, didn’t read)

If you’re facing media upload issues after adding a cache or compression plugin, don’t panic. These issues often stem from improper file permissions or server memory limitations. Adjusting permissions (typically to 755 or 644) and increasing PHP memory limits can resolve the problem in most cases. Also, review plugin settings to ensure they’re not inadvertently blocking files during optimization.

Why Cache and Compression Plugins Trigger Upload Errors

WordPress cache and compression plugins—like WP Rocket, W3 Total Cache, or Smush—are designed to improve site performance. However, these tools can alter core behaviors behind the scenes. Once installed, they might:

• Restrict access to certain directories (like wp-content/uploads).
• Overwrite or minify media-related scripts.
• Conflict with user roles or permission levels.
• Introduce aggressive browser or server caching.

The result is an inability to upload images or media files, an error stating “HTTP error” or “file could not be moved to wp-content/uploads.” Thankfully, these issues can be diagnosed and fixed.

Step-by-Step Fixes That Have Helped Users

1. Check and Reset File Permissions

File permissions control who can read, write, and execute files on your WordPress server. A caching or compression plugin might adjust these during installation or optimization routines.

Recommended permissions are:

• Folders: 755
• Files: 644

To change these:

1. Access your site via FTP or File Manager in cPanel.
2. Navigate to wp-content/uploads.
3. Right-click the folder and choose “File Permissions.”
4. Set folders to 755 and files within to 644.
5. Apply permissions recursively, checking options like “apply to enclosed files.”

2. Increase PHP Memory Limit

Media uploads can fail if the server runs out of memory—an issue exacerbated when compression plugins increase backend load. To increase WordPress memory limits:

Add the following line to wp-config.php, above the line that says “That’s all, stop editing!”:

define('WP_MEMORY_LIMIT', '256M');

If you’re on shared hosting and don’t see changes take effect, ask your host to increase your PHP memory allocation or edit php.ini (depending on access level).

3. Disable and Isolate the Plugin

Sometimes, the issue stems directly from a plugin’s settings or a bug in its latest version. Here’s how to test that:

1. Temporarily disable the cache or optimization plugin.
2. Clear both browser and server-side caches.
3. Attempt the media upload again.

If the issue disappears, you’ve likely identified the culprit. Check for plugin updates or consult its documentation for media handling preferences.

4. Exclude Upload Folders from Caching or Compression

Compression plugins, especially image optimization tools, may alter files upon upload. Configure your plugin’s settings to exclude certain directories or file types if you keep running into corrupt or blocked uploads.

For example, with WP Rocket:

• Navigate to Settings > WP Rocket.
• Click on the File Optimization tab.
• Ensure no unwanted compression is applied on uploads/ directory.

In Smush under Smush > Settings, ensure lazy loading or auto-resizing doesn’t interfere with GIFs, SVGs, or larger formats.

5. Check .htaccess Rules

Many caching plugins add directives to your .htaccess file. Misconfigurations can result in 403 Forbidden or 500 Internal Server errors during file uploads.

Look for entries like:

# BEGIN WordPress

# END WordPress

And:

# BEGIN WP Rocket

Ensure nothing here blocks file types like .jpg, .png, .svg, or .webp, especially under RewriteCond entries or mod_headers rules. If in doubt, back up the file and replace it temporarily with the default WordPress .htaccess rules.

6. Inspect Error Logs

Server logs can provide clues about what’s happening when a file upload fails. Locate your error logs either in:

• /var/log/apache2/error.log (for Apache servers)
• Or from your hosting control panel under Error Logs

Look for error entries from the minute you attempted the upload. Common culprits include:

• Memory exhausted
• Permission denied
• Access forbidden by rule

This info can guide you toward whether memory limits, file permissions, or mod_security rules are responsible.

7. Adjust PHP Upload Limits and Timeout Values

Besides memory, PHP settings might be limiting the upload size or processing time. Check with your hosting provider or, if permitted, modify php.ini, .htaccess, or wp-config.php. Recommended minimum values:

php_value upload_max_filesize 64M
php_value post_max_size 64M
php_value max_execution_time 300

In wp-config.php, you may also add:

ini_set('upload_max_size', '64M');
ini_set('post_max_size', '64M');
ini_set('max_execution_time', '300');

When All Else Fails: Ask Your Hosting Provider

Some upload limitations stem from the server layer—controlled only by your host. If you’ve tried everything above and uploads still fail, contact hosting support with the following information:

• The exact error message you receive
• Approximate file size you are trying to upload
• Plugins installed related to caching, compression, or media handling

Hosting providers often have advanced logging and access that regular users don’t, making them your most valuable ally in persistent cases.

Preventive Steps to Avoid Future Upload Issues

To prevent future issues when installing performance-related plugins:

• Back up your site before activating new plugins.
• Test uploading media immediately after installation to catch issues early.
• Follow plugin-specific setup instructions thoroughly.
• Use staging environments to test configurations before going live.

Conclusion

Media upload issues following the installation of a cache or compression plugin can be frustrating—but they’re rarely permanent or unfixable. By carefully checking file permissions, adjusting PHP memory and upload limits, and fine-tuning plugin settings, you can restore full media functionality without compromising your site’s performance goals.

WordPress is a flexible platform, but that flexibility means plugins and server settings can interact in complex ways. Understanding how and where these issues emerge puts you in better control and ensures a smoother experience for content creators and end users alike.