Feature Overview

If you enable content compression for files such as text and image files, Content Delivery Network (CDN) compresses files before transmitting them. This helps reduce CDN internal transmission traffic and the traffic for transmitting data between edge nodes and clients, which save your costs. In addition, this feature helps reduce transmission time and improve performance.

Currently, two major compression algorithms are used in the industry.

Algorithm	Algorithm Description and Characteristics	Application Scope
Gzip	The GZIP algorithm is based on the Deflate algorithm, combining Lempel-Ziv 77 (LZ77) algorithm and Huffman coding. The GZIP algorithm was designed to compress files in the Unix system in the beginning. GZIP coding for HTTP is a technology for enhancing web application performance. To use GZIP coding, web servers and clients (browsers) must support the GZIP coding method. Currently, mainstream browsers, such as IE6, IE7, IE8, IE9, FireFox, Google Chrome, and Opera, support the GZIP compression algorithm.	This compression algorithm is compatible with all browsers.
Brotli	In September 2015, Google released Brotli, a lossless compression algorithm. This algorithm can compress data using a combination of a variant of the LZ77 algorithm, Huffman coding, and second-order context modeling. This algorithm is mainly suitable for HTTP. Compared with other compression algorithms, this algorithm provides a higher compression ratio.	This compression algorithm is incompatible with some earlier browser versions.

eSurfing Cloud CDN supports the GZIP and Brotli compression algorithms.

Additional Considerations

Select a suitable compression algorithm based on your business requirements. GZIP is compatible with all browsers while Brotli is incompatible with early browsers versions.
After CDN compresses files, the MD5 values of the files are changed, if you've enabled MD5 verification for files on your origin server, please disable the file compression feature, otherwise, MD5 verification will fail.
If you enable both the page optimization feature and the GZIP or Brotil compression feature, the page optimization feature becomes invalid. CDN only compresses files but does not optimize the corresponding pages.
If you configure both the Brotli and GZIP compression algorithms for a domain name and both br and gzip fields are included in the Accept-Encoding request header, only Brotli takes effect.
It is recommended that you disable the file compression feature for common image and video file types. This feature does not take effect on these types of files because usually they are already compressed. The common image file types include PNG, JPG, and JPEG, and the common video file types include MP4, AVI, and WMV.

Procedure

Log in to the CDN console.
Go to Domain Management -> Domain List page.
On the Domain List page, find the target domain name, and click Edit in the Actions column.
Click File Processing to go to the File Compression page.
On the File Compression page, click Add . In the pop-up window, configure the parameters.
Compression Method: Select gzip or brotli. If you need to configure both methods for a domain name, repeat Step 4.

Notes:

File Types: Specify one or more file types. Example: text/xml. Separate multiple file types with commas (,). The following table provides the file types that are supported.
Minimum File Size: Specify this parameter in the value+unit format. Example: 1K, specifying that CDN compresses a file of a specified type if the file size is larger than 1 KB.

Parameter	Valid Value	Default Value	Description
Compression method	gzip and brotli.	gzip	Select gzip or brotli.
File type	Supported file types: text/xml, text/plain, text/css, application/javascript, application/x-javascript, application/rss+xml, text/javascript, image/tiff, image/svg+xml, application/json, and application/xml.	None	1. Specify one or more file types based on your business requirements. Separate multiple file types with commas (,). 2. CDN does not compress a file of a type that is not specified.
Minimum file size	Valid value ranges: 1K to 1023K and 1M to 102399M.	1K	Specify the minimum size of files that you want to compress. CDN compresses files that are larger than the specified size.

Content Delivery Network

File compression