The format parameter enables the source image to be converted (a.k.a., "transcoded") from one encoded format to another. This is useful when the source image has been saved in a sub-optimal file format that hinders performance.

Supported Output Formats

API Pattern



Parameter Description
format The output image format.

Parameter Values

Value Description
gif Graphics Interchange Format
png Portable Network Graphics
png8 Portable Network Graphics palette variant with 8-bit transparency and 256 colors
jpg JPEG
pjpg Progressive JPEG
bjpg Baseline JPEG
webp WebP
webpll WebP (Lossless)
webply WebP (Lossy)

Automatic WebP Format Selection

Automatic delivery of WebP format images via Content Negotiation can be enabled using the auto=webp parameter. This will override the format parameter in browsers that support WebP.

Although the WebP format produces images at a higher compression ratio with a lower loss of quality, it is not supported in all browsers.

Supported Input Formats

The source image can be any of the following image formats:



  1. JPEG, Progressive JPEG, WebP (Lossy) and PNG8 have a sliding quality scale that supports the quality parameter.
  2. GIF and PNG do not have a sliding quality scale. They do not support the quality parameter.
  3. A progressive JPEG pjpg is an image created using the JPEG suite of compression algorithms that will "fade in" successive waves of lines until the entire image has completely arrived. For this reason progressive JPEG's typically appear to load quicker than the Baseline JPEG jpg format.
  4. WebP support is currently only available in Google Chrome, Opera and Android Browser.
  5. Lossless compression is currently supported for WebP only.
  6. GIF transcoding is currently not supported.


Description HTML Demo
Encode to PNG - Transcode the source WebP image to a PNG. <img src="image.webp?format=png"/> Example
Advanced Examples (Combining Additional Parameters)
Description HTML Additional Param Demo
Encode to a progressive JPEG with 95% quality <img src="image.png?format=pjpg&quality=95"/> quality Example