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Image CDN

Our image CDN (formerly Photon), is an image acceleration and editing service for sites hosted on WordPress.com or on Jetpack-connected WordPress sites. That means less load on your host and faster images for your readers.

To start using the image CDN:

  1. In your blog dashboard, go to Jetpack → Settings → Writing, and in the media section toggle on the option for “Speed up images and photos
  2. You’re done! Your images will now be served dynamically from the global WordPress.com cloud.

Need some help?

How the Image CDN Works

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

Questions & Answers

  • How does the image CDN determine which dimensions to serve?
    The image CDN 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 the image CDN 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”. If you want to “refresh” an image you will need to change the name of the image. 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.comi1.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 Photon, 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.

The image CDN 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.

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