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Autoptimize speeds up your website and helps you save bandwidth by aggregating and minimizing JS, CSS and HTML.

What does the plugin do to help speed up my site?

It concatenates all scripts and styles, minifies and compresses them, adds expires headers, caches them, and moves styles to the page head, and scripts (optionally) to the footer. It also minifies the HTML code itself, making your page really lightweight.

Will this work with my blog?

Although Autoptimize comes without any warranties, it will in general work flawlessly if you configure it correctly. See "Troubleshooting" below for info on how to configure in case of problems.

What is the use of "inline and defer CSS"?

CSS in general should go in the head of the document. Recently a.o. Google started promoting deferring non-essential CSS, while inlining those styles needed to build the page above the fold. This is especially important to render pages as quickly as possible on mobile devices. As from Autoptimize 1.9.0 this is easy; select "inline and defer CSS", paste the block of "above the fold CSS" in the input field (text area) and you're good to go!

But how can one find out what the "above the fold CSS" is?

There's no easy solution for that as "above the fold" depends on where the fold is, which in turn depends on screensize. There are some tools available however, which try to identify just what is "above the fold". This list of tools is a great starting point. http://jonassebastianohlsson.com/criticalpathcssgenerator/ is a nice basic solution and http://criticalcss.com/ is a premium solution by the same developer. Alternatively this bookmarklet (Chrome-only) can be helpful as well.

Or should you inline all CSS?

The short answer: probably not (but I do).

Back in the days CSS optimization was easy; put all CSS in your head, aggregating everything in one CSS-file per media-type and you were good to go. But ever since Google included mobile in PageSpeed Insights and started complaining about render blocking CSS, things got messy (see "deferring CSS" elsewhere in this FAQ). One of the solutions is inlining all your CSS, which as of Autoptimize 1.8.0 is supported.

Inlining all CSS has one clear advantage (better PageSpeed score) and one big disadvantage; your base HTML-page gets significantly bigger and if the amount of CSS is big, Pagespeed Insights will complain of "roundtrip times". Also when looking at a test that includes multiple requests (let's say 5 pages), performance will be worse, as the CSS-payload is sent over again and again whereas normally the separate CSS-files would not need to be sent any more as they would be in cache.

So the choice should be based on your answer to some site-specific questions; how much CSS do you have? How many pages per visit do your visitors request? If you have a lot of CSS o a high number of pages/ visit, it's probably not a good idea to inline all CSS. But I do (as I have a low amount of average requests/ visitor and only a small amount of CSS as I use a pretty simple theme).

You can find more information on this topic in this blog post.

My cache is getting huge, doesn't Autoptimize purge the cache?

Autoptimize does not have its proper cache purging mechanism, as this could remove optimized CSS/JS which is still referred to in other caches, which would break your site. As from version 2.0.0 Autoptimize will display a notice on the administration pages if the cache size surpasses the half a Gigabyte mark.

You can keep the cache size at an acceptable level by either:

  • disactivating the "aggregate inline JS" and/ or "aggregate inline CSS" options
  • excluding JS-variables (or sometimes CSS-selectors) that change on a per page (or per pageload) basis. You can read how you can do that in this blogpost.

Where is the "look only in head" option?

While "look only in head" still works, it is now (since Autoptimize 2.0.0) no longer visible on the settings-page if it is not active. As long as the option is active (for JS or CSS), it will however remain visible until you deactivate it. If you're comfortable with PHP, there still are filters available to keep on using "look only in head".

So should I aggregate inline CSS/ JS?

Before Autoptimize 2.0.0, inline code was always optimized with all CSS pushed in the head-section and all JS at the end with a defer-flag. This often caused 2 problems; the priority of inline CSS got lost and inline JS could contain page- or request-specific code which broke Autoptimize's caching mechanism leading to too many cached files and the minification running over and over. This is why as from 2.0.0 by default inline code is not optimized (except for those upgrading from previous versions). Additionally, to avoid inline JS breaking because the optimized JS is not available, JS is forced in head by default. If you want to squeeze out as much performance as possible, you should indeed tick the "aggregate inline"-options and disable "force JS into head", while off course keeping an eye out for the disadvantages listed above.

What can I do with the API?

A whole lot; there are filters you can use to conditionally disable Autoptimize per request, to change the CSS- and JS-excludes, to change the limit for CSS background-images to be inlined in the CSS, to define what JS-files are moved behind the aggregated one, to change the defer-attribute on the aggregated JS script-tag, ... There are examples for many filters in autoptimize_helper.php_example and in this FAQ.

How can I use the code in autoptimize_helper.php_example?

Although you could add the code to your theme's functions.php, it would get overwritten with your next theme update. Therefor it is better to either create a helper plugin of your own or to simply use the Code Snippets plugin to manage any custom code.

Why is jquery.js not optimized

Starting from AO 2.1 WordPress core's jquery.js is not optimized for the simple reason a lot of popular plugins inject inline JS that is not aggregated either (due to possible cache size issues with unique code in inline JS) which relies on jquery being available, so excluding jquery.js ensures that most sites will work out of the box. If you want optimize jquery as well, you can remove it from the JS optimization exclusion-list (you might have to enable "also aggregate inline JS" as well or switch to "force JS in head").

How does CDN work?

Starting from version 1.7.0, CDN is activated upon entering the CDN blog root directory (e.g. http://cdn.example.net/wordpress/). If that URL is present, it will used for all Autoptimize-generated files (i.e. aggregated CSS and JS), including background-images in the CSS (when not using data-uri's).

If you want your uploaded images to be on the CDN as well, you can change the upload_url_path in your WordPress configuration (/wp-admin/options.php) to the target CDN upload directory (e.g. http://cdn.example.net/wordpress/wp-content/uploads/). Do take into consideration this only works for images uploaded from that point onwards, not for images that already were uploaded. Thanks to BeautyPirate for the tip!

Why aren't my fonts put on the CDN as well?

Autoptimize supports this, but it is not enabled by default because non-local fonts might require some extra configuration. But if you have your cross-origin request policy in order, you can tell Autoptimize to put your fonts on the CDN by hooking into the API, setting autoptimize_filter_css_fonts_cdn to true this way;


How can I force the aggregated files to be static CSS or JS instead of PHP?

If your webserver is properly configured to handle compression (gzip or deflate) and cache expiry (expires and cache-control with sufficient cacheability), you don't need Autoptimize to handle that for you. In that case you can check the "Save aggregated script/css as static files?"-option, which will force Autoptimize to save the aggregated files as .css and .js-files (meaning no PHP is needed to serve these files). This setting is default as of Autoptimize 1.8.

How does "exclude from optimizing" work?

Both CSS and JS optimization can skip code from being aggregated and minimized by adding "identifiers" to the comma-separated exclusion list. The exact identifier string to use can be determined this way:

  • if you want to exclude a specific file, e.g. wp-content/plugins/funkyplugin/css/style.css, you could simply exclude "funkyplugin/css/style.css"
  • if you want to exclude all files of a specific plugin, e.g. wp-content/plugins/funkyplugin/js/*, you can exclude for example "funkyplugin/js/" or "plugins/funkyplugin"
  • if you want to exclude inline code, you'll have to find a specific, unique string in that block of code and add that to the exclusion list. Example: to exclude <script>funky_data='Won\'t you take me to, Funky Town'</script>, the identifier is "funky_data".

Configuring & Troubleshooting Autoptimize

After having installed and activated the plugin, you'll have access to an admin page where you can to enable HTML, CSS and JavaScript optimization. According to your liking, you can start of just enabling all of them, or if you're more cautious one at a time.

If your blog doesn't function normally after having turned on Autoptimize, here are some pointers to identify & solve such issues using "advanced settings":

  • If all works but you notice your blog is slower, ensure you have a page caching plugin installed (WP Super Cache or similar) and check the info on cache size (the solution for that problem also impacts performance for uncached pages) in this FAQ as well.
  • In case your blog looks weird, i.e. when the layout gets messed up, there is problem with CSS optimization. In this case you can turn on the option "Look for styles on just head?" and see if that solves the problem. You can also force CSS not to be aggregated by wrapping it in noptimize-tags in your theme or widget or by adding filename (for external stylesheets) or string (for inline styles) to the exclude-list.
  • In case some functionality on your site stops working (a carroussel, a menu, the search input, ...) you're likely hitting JavaScript optimization trouble. Change the "Aggregate inline JS" and/ or "Force JavaScript in head?" settings and try again. Excluding 'js/jquery/jquery.js' from optimization (see below) and optionally activating "Add try/catch wrapping") can also help. Alternatively -for the technically savvy- you can exclude specific scripts from being treated (moved and/ or aggregated) by Autoptimize by adding a string that will match the offending Javascript or excluding it from within your template files or widgets by wrapping the code between noptimize-tags. Identifying the offending JavaScript and choosing the correct exclusion-string can be trial and error, but in the majority of cases JavaScript optimization issues can be solved this way. When debugging JavaScript issues, your browsers error console is the most important tool to help you understand what is going on.
  • If your theme or plugin require jQuery, you can try either forcing all in head and/ or excluding jquery.js (and jQuery-plugins if needed).
  • If you can't get either CSS or JS optimization working, you can off course always continue using the other two optimization-techniques.
  • If you tried the troubleshooting tips above and you still can't get CSS and JS working at all, you can ask for support on the WordPress Autoptimize support forum. See below for a description of what information you should provide in your "trouble ticket"

Help, I have a blank page or an internal server error after enabling Autoptimize!!

First of all make sure you're not running other HTML, CSS or JS minification plugins (BWP minify, WP minify, ...) simultaneously with Autoptimize or disable that functionality your page caching plugin (W3 Total Cache, WP Fastest Cache, ...).

In some rare cases the CSS minification component currently used by Autoptimize crashes due to a lack of resources (see detailed technical explanation here). You can in that case either disable CSS optimization, try to exclude specific CSS from being aggregated or activate the legacy minifiers which don't have that problem. The latter can be accomplished by adding this to your wp-config.php:


The "legacy minifiers" will remain in Autoptimize "for ever" and changes to wp-config.php are not affected by core-, theme- or plugin-upgrades so you should be good to go.

But I still have blank autoptimized CSS or JS-files!

If you are running Apache, the htaccess file written by Autoptimize can in some cases conflict with the AllowOverrides settings of your Apache configuration (as is the case with the default configuration of some Ubuntu installations), which results in "internal server errors" on the autoptimize CSS- and JS-files. This can be solved by setting AllowOverrides to All.

I get no error, but my pages are not optimized at all?

Autoptimize does a number of checks before actually optimizing. When one of the following is true, your pages won't be optimized: * when in the customizer * if there is no opening <html tag * if there is <xsl:stylesheet in the response (indicating the output is not HTML but XML) * if there is <html amp in the response (as AMP-pages are optimized already) * if the output is an RSS-feed (is_feed() function) * if the output is a WordPress administration page (is_admin() function) * if the page is requested with ?ao_noptimize=1 appended to the URL * if code hooks into Autoptimize to disable optimization (see topic on Visual Composer) * if other plugins use the output buffer in an incompatible manner (disable other plugins selectively to identify the culprit)

Visual Composer, Beaver Builder and similar page builder solutions are broken!!

These page builder plugins run on the frontend for logged in users and are very JavaScript intensive and should not be optimized. You can tell Autoptimize not to act on these page-builder powered pages for logged in users with this code:

function pagebuilder_noptimize() {
  if (is_user_logged_in()) {
    return true;
  } else {
    return false;

Revolution Slider is broken!

You can fix this by adding js/jquery/jquery.js to the comma-separated list of JS optimization exclusion.

I'm getting "jQuery is not defined" errors

In that case you have un-aggregated JavaScript that requires jQuery to be loaded, so you'll have to either aggregate that JavaScript (ticking the "also aggregate inline JS"-option) or add js/jquery/jquery.js to the comma-separated list of JS optimization exclusions.

My Autoptimized CSS/ JS is broken after upgrading from 1.9.4 to 2.0!

One of the bigger changes in Autoptimize 2.0 is that files that have "min.js" or "min.css" in their name are considered already minified and are only injected into the aggregated code after the actual minification, because this has an important performance-benefit. Although this has been tested rather thoroughly, it is possible that this approach does not always work. You can turn this behavior off by hooking into Autoptimize's API, like this;


Obviously you can choose to do this for only CSS, JS or both (as in example).

I use NextGen Galleries and a lot of JS is not aggregated/ minified?

NextGen Galleries does some nifty stuff to add JavaScript. In order for Autoptimize to be able to aggregate that, you'll need to tell it to initialize earlier, by adding this to your wp-config.php:


What is noptimize?

Starting with version 1.6.6 Autoptimize excludes everything inside noptimize tags, e.g.:

<!--noptimize--><script>alert('this will not get autoptimized');</script><!--/noptimize-->

You can do this in your page/ post content, in widgets and in your theme files (consider creating a child theme to avoid your work being overwritten by theme updates).

Can I change the directory & filename of cached autoptimize files?

Yes, if you want to serve files from e.g. /wp-content/resources/aggregated_12345.css instead of the default /wp-content/cache/autoptimize/autoptimize_12345.css, then add this to wp-config.php:


Can the generated JS/ CSS be pre-gzipped?

Yes, but this is off by default. You can enable this by passing ´true´ to ´autoptimize_filter_cache_create_static_gzip´. You'll obviously still have to configure your webserver to use these files instead of the non-gzipped ones to avoid the overhead of on-the-fly compression.

Where can I report an error?

You can report problems on the wordpress.org support forum. If you are 100% sure this your problem cannot be solved using Autoptimize configuration and that you in fact discovered a bug in the code, you can create an issue on GitHub.

What information should I include when requesting support

  • A description of the problem, including screenshots and information from your browser's Error/ debug console
  • URL of your blog (you can turn Autoptimize off, but should be willing to turn it briefly on to have the error visible)
  • your Autoptimize settings (including a description of changes you made to the configuration to try to troubleshoot yourself)
  • the Theme used (including the Theme's download link)
  • optionally plugins used (if you suspect one or more plugins are raising havoc)

I want out, how should I remove Autoptimize?

  • Disable the plugin (this will remove options and cache)
  • Remove the plugin
  • Clear any cache that might still have pages which reference Autoptimized CSS/JS (e.g. of a page caching plugin such as WP Super Cache)

How can I help/ contribute?

Just fork Autoptimize on Github and code away!

Requires: 4.0 or higher
Compatible up to: 4.7.3
Last Updated: 3 months ago
Active Installs: 200,000+


4.7 out of 5 stars


105 of 153 support threads in the last two months have been marked resolved.

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