Site Accelerator

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

How to Activate the Site Accelerator

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

How Site Acceleration Works

Images

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.

• It filters content but doesn’t change the info in the database.
• It currently only acts on images in posts and pages, as well as featured images/post thumbnails via the image_downsize filter.
• It will apply to old posts and new ones alike and can be turned on or off easily.

Static Files

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

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

Questions & Answers

• 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).
• 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 is narrower than the previous theme. One of the benefits of it is that it will automatically resize your images so they don’t exceed the width supported by your theme.

Limitations

• No cache invalidations – currently the images are cached “forever” and static assets will be 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 cachebusters, will not work.
• If there is an image 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, or i2.wp.com.
• We only fetch, resize, and serve gif, png, and jpg images from servers that listen on port 80 for HTTP and port 443 for HTTPS. This is 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 1000px wide and you ask for us to make it 5000px, we will serve you the original 1000px image. Upscaled images are usually of poor quality and we want to avoid that.
• If your server takes longer than 10 seconds to upload the image to our CDN, the upload will time out and your image will appear to be broken. Try to upload a differently-named image with a smaller file size if this happens.

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.

This 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 magic image service. Abuse of Jetpack or violation of the WordPress.com Terms of Service could result in suspension of your site from WordPress.com-connected services.

Privacy Information

This feature is deactivated by default. If you ever need to deactivate this feature, you can toggle them off under the Performance & speed section from Jetpack — Settings — Writing in your dashboard.