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CDN:Format conversion

Last Updated:Jul 14, 2026

If an image is too large or displays incorrectly on certain platforms, use format conversion to convert it to the WebP format or to a specified format.

CDN image editing, DCDN image editing, and Object Storage Service (OSS) Image Processing (IMG) are three separate features. Image editing is free of charge until further notice.

Adaptive WebP

WebP is an image file format that supports both lossy and lossless compression. CDN supports an automatic conversion to WebP feature. When this feature is enabled, CDN checks the Accept request header. If the header contains image/webp, CDN automatically converts images in other formats to the WebP format for caching. To enable this feature, see Image processing operations.

Important After you enable automatic conversion to WebP, the cache hit ratio decreases. It automatically increases after a short period of time. Do not enable this feature during peak hours.

Example

The following Accept header is an example. The actual header may vary. In this example, the header contains image/webp, which indicates support for automatic conversion to WebP.

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9

Format conversion parameters

Action: format

Value

Description

jpeg

Converts the source image to JPEG format.

png

Converts the source image to PNG format.

webp

Converts the source image to WebP format.

bmp

Converts the source image to BMP format.

gif

Preserves the GIF format if the source image is a GIF. Otherwise, the format is unchanged.

tiff

Converts the source image to TIFF format.

jp2

Converts the source image to JPEG 2000 format. The file extension is .jp2.

Converting between formats may increase file size because different formats use different compression algorithms. For example, converting JPEG to WebP, JPEG to PNG, or PNG to WebP can produce a larger output. To reduce the output file size, set the quality parameter to lower the image quality.

Example

To convert the source image to BMP format, the image processing URL is: http(s)://example.com/image_01.png?image_process=format,bmp