General Questions

  • Why Swift Performance?

    Swift Performance is an all-in-one performance booster plugin. It provides everything that you need to speed up your site (replacing several optimization plugins), and improve user experience.

    Swift Performance is already running on 2000+ websites and based on our customers’ feedback it is the fastest performance plugin on the market.

    With the Setup Wizard you can easily configure the plugin.

  • What is the difference between premium and lite versions

    Swift Performance Lite has limited features, and we are not planning to add new features to Lite version. Of course bugfixes, and compatibility updates will be released, but new features will be available only in premium version.

    We also provide premium support for premium version, which means we are happy to help to configure the plugin, find any speed issues, even add new features to solve your exact speed issues. For lite version we provide only basic support (to keep it compatible and fix major 3rd party conflicts)

  • Do you provide renewal discount?

    The plugin published under GPLv2 license, however the API, the updates, and the support is subscription based. Currently we provide monthly, quarterly and yearly packages.

    You can save a notable amount if you choose longer subscription period, but we currently do not provide additional discounts by default.

  • Is the Image Optimizer really unlimited?

    Yes, the premium version comes with an unlimited Image Optimizer, which means it is truly unlimited, and already included in your subscription.

    You can optimize all of your images without any additional fee. There is a technical 10Mb size limit, however with normal usage you shouldn’t have 10Mb images on your site.

  • API Connection Failed

    If you already set the purchase key, and you see on dashboard that API connection was failed, that usually means that your hosting is blocking outgoing connections.

    Please contact to hosting support, and ask them to whitelist api.swteplugins.com and api2.swteplugins.com

    If you get Purchase key is invalid message when you try to set purchase key in settings can be caused by blocking outgoing connections as well.


  • I get a javascript error when I enable minify for scripts

    Some 3rd party theme/plugin scripts contain invalid code (eg missing semicolon), which can be fixed by the browser, but if you minify them and multiple commands will be moved into one line it can cause issues.

    You can notify the 3rd party theme/plugin developer about the issue, however in premium version you can enable the Minify with API feature as well, which is using a more complex minify engine which can also fix the invalid code on the fly.

  • FOUC - I have flash of unstyled content issue

    Probably some of your CSS files contains an invalid line (eg unclosed media query), which can break the Critical CSS generation.

    In most cases it caused by custom styling, but plugin and theme styles can also cause the issue. Try to exclude files one-by-one from merging (Settings > Optimization > Styles > Exclude Styles) to find what is causing the issue.

  • I got a blank page, or just a simple line (eg Copyright 2018)

    Some of your javascript contains a document.write command. When scripts are combined (especially if Async Execute is enabled) this command can overwrite the content of the whole page.

    You can simply exclude the problematic script in Settings > Optimization > Scripts > Exclude Scripts

    You can also exclude inline scripts which contains the document.write command, just add a rule to Settings > Optimization > Scripts > Exclude Inline Scripts: “document.write”

  • I still get ``Render Blocking CSS/JS`` issue in Google PageSpeed Insights

    Usually you will get “Render Blocking” issue if the Critical CSS is not enabled, or there is something in the viewport what needs javascript for rendering (eg slider or animated elements).

    You can enable Disable Full CSS feature, but please note, that some javascript added styles can be missing.  You should check all pages and if it is necessary, you can also add Extra Critical CSS


    PageSpeed Insights is a good tool to get recommendations to improve performance, but you don’t need to fix every warning. You can maximize the scores in testing tools, but don’t forget the goal: speed up the loading/rendering time.

  • Combined CSS or JS file is not compressed

    The problem is that the combined CSS or JS file exceeds the max GZIP size limit. Increase the limit to apply compression for these files.

    If you have issues with the combined CSS, you can also try the Disable full CSS option, but if you do, you should check all pages, because some javascript added classes can be missing from Critical CSS.

    Alternatively you can exclude some CSS/JS files from merge, but of course it is not the best solution

  • Images are blurry, or they won't load

    If you enable Lazyload for images it will load a placeholder image (a very small version of the original one, or a 1×1 pixel transparent gif), and load the full image with javascript when it is almost in the viewport.

    If you have a javascript conflict this will may broken. Please check the javascript console to see what cause the issue.

    As a quick fix you can disable Merge Scripts option

  • First pageload is very slow

    Generating Critical CSS can take some time based on your theme and plugins. To avoid increased first page load times you should enable Optimize Prebuild Only or  Optimize in Background features.

  • High CPU Usage

    While the plugin is generating the cache the CPU usage can be higher than usual. If CPU usage is constantly higher you may need check the configuration. It is recommended to enable Settings > Optimization > General > Optimize Prebuild Only and Settings > Caching > Warmup > Prebuild Cache Automatically

    Generating Critical CSS is the most CPU intensive process. It is also recommended to enable Settings > General > Compute API to reduce CPU usage.


  • Cache is not working

    If you enabled caching but you can’t see cached pages on status page it can be caused by multiple things:

    • You are using a 3rd party cache solution (eg Cloudflare, Varnish, etc) which caches the page before Swift Performance can cache it. Note: Swift Performance supports most of these solutions, please configure them on Caching and/or CDN tabs in the Settings in order to work
    • The cache folder is not writable. First you should reset Caching > General settings. If that did not solve the problem you can check is there are any files in the specified cache folder. If there are files, but the site doesn’t load from cache, it may be the htaccess/nginx rewrite rules are not set. Please check htaccess or nginx conf and copy the rules from plugin’s dashboard.
  • Strange redirects

    If you have strange URLs in your analytics or you can see that the site redirects to an URL like this:


    This is caused by an improper order of htaccess rules. Probably you are using a force SSL or force www/non-www rule in htaccess. Please remove these rules from htaccess, and insert them in Settings > General > Tweaks > Custom htaccess.

  • Prebuild is not working

    If you can see on the plugin’s dashboard, that the plugin tries to prebuild cache, and load the URLs but the pages aren’t cached, it can be a cache issue (see above), or an error breaks the prebuild process.

    Please enable logging in Settings > General and set the loglevel to warning. After that please try to run the prebuild again, and check the plugin’s log.

    If the Prebuild process won’t start at all, it can be a WP Cronjob issue. If you are using customized WP Cronjobs, please try to disable them and try it again.

  • How to optimize get_refreshed_fragments

    WooCommerce get_refreshed_fragments AJAX request sometimes can slowdown page loading. There are some plugins and snippets which offers disabling it, however it can cause conflicts.

    Regarding that for empty cart you don’t need to refresh fragments, so to optimize it you can enable Cache Empty Minicart in Settings > Caching > WooCommerce > Cache Empty Minicart

Have questions? Search our FAQ knowledgebase.