WP Super Cache

Posted on July 21, 2023 by bob matyas

WP Super Cache is a plugin maintained by the Jetpack team that generates static html files from your dynamic WordPress blog. After a html file is generated, your webserver will serve that file instead of processing the comparatively heavier and more expensive WordPress PHP scripts.

Getting Started

Reporting Bugs and Requesting Features

WP Super Cache is developed out of the Jetpack repository on GitHub. Please report bugs and make enhancement/feature requests there:

Make sure to select “Super Cache” as the affected plugin.

Advanced Topics

Developer Documentation

Scope of Support

WP Super Cache is an open-source plugin maintained by Automattic. We provide detailed documentation on how to install, set up, and run WP Super Cache. If you run into trouble, we have an FAQ as well as a support forum where you can seek help from the community. Happiness Engineers from Automattic monitor the forum and will answer general questions about installation, standard configuration, and use. While we can’t answer every question, we’ll do our best to point you in the right direction.

We cannot assist with:

  • Server configurations and optimizations
  • Theme-related issues: WP Super Cache is designed to be compatible with a majority of WordPress themes. However, we can’t guarantee full compatibility with every theme. In the case of conflicts, please work with the developers or support team of the conflicting plugin.
  • Third-party plugin conflicts: We can’t ensure compatibility with other WordPress plugins. In the case of conflicts, please work with the developers or support team of the conflicting plugin.
  • Customizations and custom configurations.
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Site Accelerator

Posted on November 5, 2018 by Kellie Hodgins

Jetpack’s Site Accelerator (a.k.a. Jetpack CDN) helps your pages load faster by allowing Jetpack to optimize your images and serve them alongside static files (like CSS and JavaScript) from our global network of servers.

Note: “Photon” is now part of Site Accelerator.

For general features and FAQs, please see our CDN features here.

How to Activate the Site Accelerator

  1. In your site’s dashboard, go to Jetpack → Settings → Performance.
  2. In the Performance & speed section, toggle on

How Site Acceleration Works

Image load times

Our Image CDN (formerly Photon) is an image acceleration and editing service. That means that we host your images from our servers, alleviating the load on your server and providing faster image loading for your readers.

Static file load times

We host static assets like JavaScript and CSS shipped with the WordPress core, Jetpack, and WooCommerce from our servers as a content delivery network (CDN), alleviating the load on your server.

  • It filters the URLs of assets that are loaded with every WordPress page.
  • It only acts on assets shipped with WordPress core, Jetpack, and WooCommerce. Theme and plugin assets are not supported at this time.

Limitations

  • No cache invalidations. Currently, static assets are tied to the public version of WordPress, Jetpack, or WooCommerce that you’re using. For images, if you want to “refresh” an image, you will need to change its file name. Adding random query arguments, commonly known as “cache busters,” will not work.
  • It is not possible to automatically purge all images from a site. If there is an image no longer on your server that you’d like us to purge, please contact us with a direct link to the file as it appears on your site. These will begin with i0.wp.com, i1.wp.com, i2.wp.com or i3.wp.com. Since images can only be purged manually by individual URL, there is a limit to the number we can purge.
  • We only fetch, resize, and serve GIF, PNG, JPG, and WebP images from servers that listen on port 80 for HTTP and port 443 for HTTPS. This applies to about 99.99% of the web servers in the world. If you are having issues, please try using the jetpack_photon_reject_https filter.
  • We will not “upscale” an image in most circumstances. If your original image is 1,000px wide and you ask for Jetpack to make it 5,000px, we will serve the original 1,000px image. Upscaled images are usually of poor quality, and we want to avoid that.
  • If your server takes longer than 10 seconds when an image is being retrieved for our CDN, the process will time out and your image will appear to be broken. Try to upload a differently-named image with a smaller dimension or file size if this happens.
  • It’s not possible to choose or limit where in the world your images will be served from. We have servers placed all over the world, and which server will load your image is dependent on a variety of factors, including the visitor’s location.
  • Site Accelerator does not support animated PNGs.

Themes and plugins can also use the Photon API to transform images using GET query arguments. Developers will find Photon API examples and documentation on developer.wordpress.com.

Site Accelerator is only allowed to be used by sites hosted on WordPress.com or on Jetpack-connected WordPress sites. If you move to another platform or disconnect Jetpack from your site, please also switch to another image CDN service. Any abuse of Jetpack or violation of the WordPress.com Terms of Service could result in the suspension of your site from WordPress.com-connected services, including Site Accelerator.

FAQ

Can I use your Site Accelerator with audio or video files?

Site Accelerator does not serve audio (.mp3, .wav, .flac, etc.) or video (.mp4, .wmv, .flv, etc.) files. If you’d like to host videos on our CDN, check out our Video Hosting feature.

How does Site Accelerator determine which dimensions to serve for an image?

It looks at the img element’s width and height attributes and then serves an image resized to those dimensions or to the width of the containing element (whichever is smaller). By default, Jetpack will constrain images to the larger of the size indicated when adding the image to a post or to your theme’s “content width” setting. If one isn’t set, Jetpack will default to 1,000px. This is to help ensure that sites are not trying to serve images larger than what the theme intended to be able to display.

Is there any way to keep the “width” and “height” attributes in the CDN-generated HTML?

We remove the width and height arguments to prevent your images from skewing when the resized image doesn’t have the same dimensions as the original. This is particularly important when you switch from one theme to another, and the new theme might be narrower than the previous one. One of the benefits of this is that we will automatically resize your images so they don’t exceed the width supported by your theme.

What happens to my images if I disable Image Accelerator?

No worries! Your images will continue to work just fine, they will just start loading from your webhost’s server again instead of ours. Please note that it could take a few minutes for these changes to take place.

Once Site Accelerator has been enabled, can I delete the images from my server?

No! Your images need to remain on your server for the CDN to work correctly. Any images that are removed from your server will eventually “expire” and be removed from the CDN.

I enabled/disabled Site Accelerator and the images are broken!

  • As a first step, wait a few moments and then load your site in a completely different web browser than you normally use to make sure it’s not just your browser cache interfering with the URL change. It can take a few minutes for these changes to be reflected on your entire site.
  • Next, check that your Jetpack connection is working properly.
  • Still not working? It is possible that there may be another plugin on your site conflicting with Site Accelerator. Please try to disable all of your plugins except Jetpack, then try checking your images again. If they are displaying properly, we’ll know that another plugin is interfering. You can find out which plugin is the culprit by enabling each plugin one by one and checking images after each one.
  • Finally, if it still isn’t working after disabling your plugins, it may be the theme. To test this, you can switch to one of the default themes such as Twenty Seventeen. If the issue is resolved, then you know it’s a problem with the theme, and you’ll need to contact the theme author for further assistance.
  • No luck? Please reach out to us for more support.

Still need help?

Please contact support directly. We’re happy to advise.

Privacy Information

Site Accelerator is deactivated by default. You can toggle the feature on or off under the Performance & speed section from Jetpack → Settings → Performance in your dashboard.

Data Used
Site Owners / Users

While not actively used in the delivery of this functionality, EXIF data may exist (and be accessible to site visitors) in any of the images that you upload to your site.Additionally, for activity tracking (detailed below): IP address, WordPress.com user ID, WordPress.com username, WordPress.com-connected site ID and URL, Jetpack version, user agent, visiting URL, referring URL, timestamp of event, browser language, country code.

 Site Visitors

None.
Activity Tracked
Site Owners / Users

We track when, and by which user, the feature is activated and deactivated.

 Site Visitors

None.
Data Synced (Read More)
Site Owners / Users

We sync a single option that identifies whether or not the feature is activated.

 Site Visitors

None.
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Performance

Posted on December 20, 2017 by A. Jay

Jetpack offers a growing range of features to help you improve how fast your site loads.

Jetpack includes features which improve performance on mobile devices and slow or unreliable connections, or with large amounts of site content.

Here are some resources to help get you started:

  • Using the Optimize CSS Loading Feature in Jetpack Boost - Jetpack Boost is equipped with a range of features aimed at increasing your website’s speed. Among these features is Optimize CSS Loading, which shifts crucial style information to the beginning of the page, enabling faster content display. This technique, known as Critical CSS, is instrumental in enhancing your site’s user experience and overall performance. What […]
  • Improve your Site Speed Score - Give your visitors the best experience possible by ensuring that your site loads quickly and reliably. Jetpack tools such as Site Accelerator and Jetpack Boost can help. In some cases, you may want to make additional improvements. This guide offers some suggestions on how to improve your site’s speed and performance. Measure your site speed […]
  • Jetpack Boost: Image Performance Guide - The image performance guide is a tool that can help you ensure that the images used on your site’s pages and posts are the right size. Using the Image Performance Guide Overview Testing with different devices and settings The Image Performance Guide shows you information about your images as they appear on the current device. […]
  • Automate Critical CSS with Jetpack Boost - When you upgrade to the paid version of Jetpack Boost, you can automatically generate critical CSS every time you make a change. It replaces the traditional locally generated Critical CSS and the need to do it manually. After subscribing to the Jetpack Boost plan, you will see a confirmation page. Click Continue to go to […]
  • Jetpack Boost: Console errors - One of the main features of the Jetpack Boost plugin is called “Optimize CSS Loading”. When you enable this feature, the plugin figures out the most important CSS rules to display first (called Critical CSS) for different sections of your website. This Critical CSS helps pages display your content sooner, so your users don’t have […]
  • Jetpack Boost - Jetpack Boost provides one-click optimizations that supercharge your WordPress site’s performance and improve web vitals scores for better SEO.
  • Progressive Web Application (PWA) - Speed up and improve the reliability of your site using the latest in web technology.
  • Site Accelerator - Jetpack's global Content Delivery Network (CDN) optimizes files and images so your visitors enjoy the fastest experience regardless of device or location.
  • Performance - Jetpack offers a growing range of features to help you improve how fast your site loads. Jetpack includes features which improve performance on mobile devices and slow or unreliable connections, or with large amounts of site content. Here are some resources to help get you started:
  • Lazy Loading Images - Lazy Images are now deprecated.
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Lazy Loading Images

Posted on December 20, 2017 by paulinahetman

Note: Jetpack’s Lazy Loading feature was first introduced in 2018. At the time, few other tools offered such functionality. It offered a much needed performance boost to WordPress sites, especially those with a large number of images.

A couple of years later, a new lazy loading web standard was introduced, and WordPress itself started supporting this standard. Today, modern browsers all support lazy loading, and WordPress itself comes with built-in lazy loading functionality for images and videos.

Considering this positive change, Jetpack’s Lazy Loading feature is no longer necessary. You have the option to disable it on your website, and you will immediately begin benefiting from the native lazy loading feature offered by WordPress itself.

To facilitate this transition, Jetpack’s feature will be deprecated and eventually removed from both the Jetpack plugin and the Jetpack Boost plugin in November 2023.

Lazy Loading Images makes pages load much faster by only loading visible images, waiting to load images that are off-screen as you scroll down. This feature can improve site performance, and is especially great for users in low-bandwidth or expensive-bandwidth environments, such as users on mobile devices. This feature is compatible with WordPress core’s lazy-loading images feature.

Activating or deactivating Lazy Loading Images

  1. Navigate to Jetpack → Settings → Performance.

  2. Scroll to the Performance and Speed section.

  3. Click the toggle to activate / deactivate Lazy loading for images.

How does the Lazy Loading Images feature work?

The Lazy Loading images feature filters the post content and modifies image tags so that the src attribute loads a transparent placeholder image. For example, <img src="https://jetpack.com/image.jpg" /> would become <img src="https://jetpack.com/placeholder.jpg" data-lazy-src="https://jetpack.com/image.jpg" /> .

When JavaScript then loads, it will look for all images in the current view and replace the src attribute with what is in data-lazy-src. This also occurs as the user scrolls down the page and images come into view.

How does the Lazy Loading Image feature improve site performance?

By default, when a web page loads, it attempts to also load all the images that it sees in the source. For a visitor using a desktop browser, the time and bandwidth necessary to load that page may not be an issue.

With mobile usage of the Internet now surpassing that of the desktop, the majority of our users are likely accessing our content with mobile devices. For mobile visitors, where the view is much narrower and bandwidth is a more significant concern, this full loading can be problematic. That’s using bandwidth to load images that they may not even want to see.

By lazy loading images, those images will only load when they actually appear on-screen, reducing bandwidth usage by as much as half of what is used without lazy loading images enabled.

Customizing Lazy Loading Images

These filters allow you to tweak the lazy image functionality. The code snippets below provide examples of some of the filters included in the lazy images feature. You can add these code snippets to a functionality plugin or to your theme’s functions.php file.

Disabling Lazy Loading Images

Lazy loading images are set to be enabled for your entire site by default. You can use the filter lazyload_is_enabled to customize when lazy loading should be enabled. For example, if you don’t want lazy loading images on a certain page, you could hook in and disable lazy loading images for that page.

Use a Different Placeholder Image

By default, Jetpack will load a 1×1 transparent GIF, but certain implementations may call for something else. The filter lazyload_images_placeholder_image will allow you to specify your own placeholder image.

Modify the Attributes of a Lazy-Loaded Image

The jetpack_lazy_images_new_attributes filter will allow you to modify the attributes for a lazy-loaded image as the content is filtered. This is to allow for changes based on more customized and specific implementations.

Exclude Specific Images

You can instruct Lazy Loading Images to skip any image by adding the skip-lazy CSS class to an image.

You can also use jetpack_lazy_images_blocked_classes filter to set additional CSS class names that shouldn’t be lazy-loaded. For example:

function mysite_customize_lazy_images( $blocked_classes ) {
    $blocked_classes[] = 'my-header-image-classname';
    return $blocked_classes;
}

add_filter( 'jetpack_lazy_images_blocked_classes', 'mysite_customize_lazy_images' );

Lazy Loading Images and Jetpack Boost

If you use the Jetpack Boost plugin’s Lazy Loading Image feature, turning on and off the Lazy Loading Images feature will also turn on and off the Lazy Loading Image feature in Jetpack Boost.

Lazy Loading Images and Safari

To fix issues with lazy-loaded images in the Safari browser, please update Jetpack.

Still need help?

Please contact support directly. We’re happy to advise.

Privacy Information

This feature is deactivated by default. If you ever need to activate this feature, you can toggle the Lazy load images setting in the Speed up your site section from Jetpack → Settings → Performance in your dashboard.

Data Used
Site Owners / Users 

 

For activity tracking (detailed below): IP address, WordPress.com user ID, WordPress.com username, WordPress.com-connected site ID and URL, Jetpack version, user agent, visiting URL, referring URL, timestamp of event, browser language, country code.

 Site Visitors 

 

None.
Activity Tracked
Site Owners / Users 

 

We track when, and by which user, the feature is activated and deactivated.

 Site Visitors 

 

None.
Data Synced (Read More)
Site Owners / Users 

 

We sync a single option that identifies whether or not the feature is activated.

 Site Visitors 

 

None.

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