ShortPixel Image Optimizer (SPIO) was designed to use as few resources as possible and only be run when users with certain roles are logged in. This means that when someone is visiting your website the load speed should be virtually the same, whether SPIO is optimizing images at that very moment or not. However, some sites experience different types of speed issues.
Important notes:
- The number 1 reason of speed issues on your website is your hosting provider. It is very common to experience slowness on low-cost shared hosting providers. Consider migrating to a better-performing server.
- If SPIO is used alone, it has practically no effect on the loading speed of websites. PluginTests has checked and confirmed this here. PluginTests is an independent testing platform for plugins that evaluates both memory consumption and possible effects on page speed metrics.
- Dashboard slower than usual: If you notice, while logged in as admin (for example), that the dashboard is slower than usual, it could be because ShortPixel is running in the background. If you want to make sure that SPIO is the cause of that, just stop the optimization process in Media Library/Bulk ShortPixel and see if it makes any difference.
- High CPU, disk, or RAM usage: In years of experience we have learned that some sites will have a higher resource usage than others depending on the number of visitors, plugins, available resources, etc. Here's a list of possible causes and solutions.
- The option Optimize Retina images is active: During image processing, this adds to disk usage. This option is located on Settings > ShortPixel > Advanced, and if there is no reason to keep it on, we recommend turning it off.
- The option Optimize other thumbs is active: During image processing, this adds to disk usage. This option is located on Settings > ShortPixel > Advanced, and if there is no reason to keep it on, we recommend turning it off.
- There are too many thumbnails associated with each image: WordPress by default generates 5 to 10 thumbnails; if you have more than 10 thumbnails, you should consider excluding some thumbnails from optimization. You have to take into account that each image needs to be replaced, have a backup created, etc, therefore the more thumbnails you have, the more operations ShortPixel has to do and the more load your server will have.
- The option Convert PNG images to JPEG is active: During image processing, this adds to RAM usage. If a PNG file is big, it can easily use more than 100 MB per process. So if there are a few of those optimizing, it can happen that the server gets overloaded.
- (Only applicable prior to SPIO version 5.0) The option Process in front-end is active: When an image is getting optimized and people visit your site, each of them will fire off an AJAX request to check upon status. This can add up to your CPU usage quite fast if you have lots of visitors, and in our experience is the option that can cause the most CPU usage issues. This option is located on Settings > ShortPixel > Advanced, and if there is no strong reason to keep it on, we recommend turning it off.
- Too many MySQL queries: Why does ShortPixel make a lot of MySQL queries? Should I worry?