Site Accelerator (previously Photon) is an image acceleration and modification service for Jetpack-connected WordPress sites. Converted images are cached automatically and served from the CDN. Images can be cropped, resized, and filtered by using a simple API controlled by GET query arguments. When Site Accelerator is enabled in Jetpack, images are updated on the fly.

We want to create the best image manipulation and acceleration service in the world for WordPress users. Site Accelerator is only allowed to be used by sites hosted on, 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. We can’t promise it will continue to work if you stop using WordPress or Jetpack. Abuse of Jetpack or violation of the Terms of Service could result in suspension of your site from services.



  • Open source! Available via SVN at and on Trac at
  • Fast! Site Accelerator utilizes multiple levels of caching, including a globally distributed CDN to make sure images are served as fast as possible.
  • All images are compressed on the fly using either a combination of pngquant and OptiPNG or jpegoptim. Lossless compression is available by specifying a quality setting of 100 in the query arguments.
  • Multiple domains. In order to take advantage of parallel downloads we support multiple sub-domains for Site Accelerator . If you tend to have many images per page you can split them across,, and To take use of caching, it can be useful to use the same sub-domain for files in subsequent calls.
  • SSL support. You can use Site Accelerator on SSL pages without mixed content warnings. Just use https://i{0,1,2} instead of http://i{0,1,2}

Supported query arguments

wwidth (px)w=50
hheight (px)h=50
cropcrop x,y,w,h (defaults to %)crop=5,10,20,40
resizeresize and crop to given dimensions (px)resize=250,300
fitkeep aspect ratio, but fit to within given box (px)fit=100,100
lbadd letterboxing, color code is optional (it’s black by default)lb=300,250,1A4E9F
ulbremove letterboxing (auto detects the letterbox color)ulb=true
filterapply various imagefilter() filtersfilter=grayscale
brightnessadjusts brightnessbrightness=100
contrastadjusts contrastcontrast=50
colorizeapplies a color huecolorize=255,0,0
smoothsmoothes out the imagesmooth=2
zoomsize images for high pixel ratio deviceszoom=2
qualitysets the quality for JPEG imagesquality=50
stripremoves metadata from JPEG imagesstrip=all

Also see the Site Accelerator API page for more detailed explanations and examples.

Example plugin developer checks

  • To determine if Jetpack is installed and can generate Site Accelerator URLs:
    class_exists( 'AutomatticJetpackImage_CDNImage_CDN' )
  • To determine whether Site Accelerator is an active Jetpack module:
    class_exists('AutomatticJetpackImage_CDNImage_CDN' ) && AutomatticJetpackImage_CDNImage_CDN::is_enabled()


  • 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.
  • We only fetch, resize, and serve gif, png, webp, jpeg, 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.
  • We will “upscale” an image in some circumstances. However if your original image is smaller than the upscale limit and you request to make it larger than the upscale limit, we will serve you the original unaltered image (Note: 2000px is the upscale limit for all images except GIFs, which is 1000px). Upscaled images are usually of poor quality and we want to avoid sending large pixelated images.
  • Some animated gifs break if resized or transformed via Site Accelerator.
  • The zoom parameter is clamped between 1 and 10 and above 3 it is also limited to increments of 0.5.
  • Site Accelerator will not fetch and process images larger than 55 Megabytes.

Terms of Service

  • Use of this service is for users of the Jetpack by only, and may be used by sites hosted on, or on Jetpack-connected WordPress sites. If you move to another platform, or disconnect Jetpack from your site, we can’t promise it will continue to work.
  • Abuse of the Jetpack by Terms of Service could result in the suspension of your site from services. By enabling Site Accelerator, you agree to be responsible in what you publish; in particular be sure that you don’t use the service for prohibited items (things like spam, viruses, or hate content). reserves the right, in its sole discretion, to temporarily or permanently revoke your ability to use and access Site Accelerator, with or without notice.