Troubleshooting

Images aren't being optimized

Check system status. Go to Compresso > Dashboard and look at the System Status section. If compression binaries (like jpegoptim or cwebp) show warnings, they may not be installed on your server. Contact your hosting provider to install them, or Compresso will fall back to PHP's GD library.

Check auto-optimize is enabled. Go to Compresso > Settings and confirm Auto-Optimize on Upload is turned on.

Check file permissions. Your wp-content/uploads directory needs to be writable. If Compresso can't write to the file system, optimization will fail silently. Check your logs at Compresso > Logs for permission errors.

Check file size limits. If you have Skip large images enabled, files over your configured limit (default 10MB) will be skipped. Same for Skip small images if you've set a minimum size.

WebP images aren't being served

Is WebP conversion enabled? Check Compresso > Settings — both WebP Conversion and a WebP Delivery method must be enabled.

Clear your cache. Browser cache, caching plugins (WP Super Cache, W3 Total Cache, LiteSpeed, etc.), and CDN cache all need to be cleared after enabling WebP delivery.

Check the delivery method. If you're using .htaccess rewrite on a non-Apache server (Nginx, LiteSpeed), it won't work. Switch to Picture tags or JavaScript delivery instead.

Verify in browser DevTools. Open your site, press F12, go to the Network tab, filter by "Img", and check the Type column. If it shows webp, delivery is working even if the URL still shows .jpg.

Bulk optimization is stuck or not progressing

Check Action Scheduler. Compresso uses Action Scheduler (not WP-Cron) for all background processing. Go to Tools > Scheduled Actions in your WordPress admin and look for compresso actions. If they're showing as failed or stuck pending, your Action Scheduler may not be running properly.

Memory or timeout limits. Large images can exceed your server's PHP memory limit or execution time. Check Compresso > Logs for timeout or memory errors. If you see them, ask your host to increase memory_limit and max_execution_time in your PHP configuration.

Lazy loading causes layout shifts

Enable Auto Dimensions. Layout shifts happen when the browser doesn't know an image's size before it loads. Enable Auto Dimensions in Compresso settings to add width and height attributes automatically.

Set "Skip first N images." Set this to 2–3 so above-the-fold images load immediately instead of lazily.

Images look lower quality than expected

Check your compression mode. If you're using Aggressive mode, try switching to Balanced for a better quality-to-size ratio.

Use Visual Diff to compare. If you have Compresso Pro, use Visual Diff to compare the original and optimized versions side by side. Zoom in to check for artifacts.

Restore and re-optimize. If a specific image looks bad, restore it and re-optimize with higher quality settings or Lossless mode.

The plugin is slow or causing timeouts

Reduce concurrent processing. If bulk optimization is causing server strain, pause it during peak traffic hours and resume during off-peak times.

Check your hosting plan. Shared hosting plans often have strict resource limits. Image optimization is CPU-intensive — if you're optimizing thousands of images, consider upgrading to a VPS or managed WordPress host.

Check log level. If you have logging set to Debug, it generates a lot of database writes. Switch to Info or Warning for normal operation.

Can't find the backups directory

Compresso stores backups in wp-content/uploads/compresso-backups/. If this directory doesn't exist, backups may not have been created yet (they're created on first optimization).

If the directory exists but seems empty, check that your file manager is showing hidden files — some hosting panels hide directories starting with certain prefixes.

Still stuck?

1. Check Compresso > Logs with the log level set to Debug — this gives the most detailed information about what's happening
2. Look for error patterns — file permission issues, missing binaries, or timeout errors are the most common causes
3. Try optimizing a single image manually to isolate whether the issue is with a specific file or the system overall