CDN:Configure HTTP response headers

Scenarios

• Invalid value of Content-Type: If the value of Content-Type that is returned by the origin server does not match the actual type of the content, the clients may fail to parse the content. For example, if an HTML file is incorrectly marked as plain text, you can rewrite the response header.

  In this example, change Content-Type: text/plain to Content-Type: text/html.

• Cache policies: If you want to maintain precise cache control, you can adjust the Cache-Control or Expires response header. This optimizes the update frequency and hit rate of the cached content.

  In this example, change Cache-Control: max-age=3600 to Cache-Control: max-age=86400 to extend the cache validity period. For more information, see Default cache rule and priorities of cache rules.

• CORS: If you want to allow web applications from other domains to access resources hosted on Alibaba Cloud CDN, set Access-Control-Allow-Origin and other related CORS headers on the origin server. These settings ensure that Alibaba Cloud CDN provides correct response headers to the clients when a cross-origin request is initiated. For more information, see Configure CORS.

  Examples:

  • Access-Control-Allow-Origin: *: Access from all domains is allowed.

  • Access-Control-Allow-Methods: GET, POST, OPTIONS: The HTTP methods that clients are allowed to use are GET, POST, and OPTIONS.

• Compression: If compression is supported but disabled for the origin server or the compression algorithm that is used is not optimal, you can configure the Accept-Encoding response header to enable the origin server to use the optimal compression method.

  In this example, change Accept-Encoding: gzip, deflate to Accept-Encoding: br to use Brotli compression first. For more information, see Configure Brotli compression.

• Redirection: If the origin server needs to redirect a request to a different URL, you can use this feature to set the correct redirect response header. For more information, see Configure 301/302 redirection.

  Example: Location: https://www.example.com/new-page.html. The value of the Location header specifies the new address of the requested resource after a POP receives the HTTP status code 301 or 302 that is returned by the origin server.

• Custom origin response headers: If you want the origin server to return custom HTTP headers for special requirements, you can configure custom HTTP response headers.

Usage notes

If multiple rules are configured for the same header, the rules are executed from top to bottom in the configuration list. Examples:

• Configuration 1: Add the cache-control: max-age=3600 response header.

• Configuration 2: Add the cache-control: no-cache response header.

In the preceding combined configurations, Configuration 2 takes effect.

Procedure

1. Log on to the Alibaba Cloud CDN console.

2. In the left-side navigation pane, click Domain Names.

3. On the Domain Names page, find the domain name that you want to manage and click Manage in the Actions column.

4. In the left-side navigation tree of the domain name, click Origin Fetch.

5. Click the Custom Response Headers tab.

6. Click Customize.

7. Configure the parameters in the Custom Response Headers dialog box.

   Important

   When different operations are performed on the same response header at the same time, the operations have different priorities. The operations are prioritized in the following descending order: Replace > Add > Change or Delete. For example, if you perform the Add and Delete operations on the same response header at the same time, the response header is added and then deleted.

   Parameters of the Add operation

   

   Parameter	Example	Description
   Operation	Add	This operation adds a response header to response messages from an origin server.
   Response Header	Custom Response Header	You can select a preset header or select Custom Response Header from the Response Header drop-down list to specify a response header.
   Header Name	x-code	The name of the custom response header is x-code.
   Header Value	key1	You can specify multiple values for a response header. Separate the values with commas (,).
   	key1,key2
   Allow Duplicates	Yes	Yes: You can add duplicate response headers. Example: x-code:key1 and x-code:key2. No: The latest header value overwrites the existing header value that uses the same header name. For example, if you add x-code:key1 and then add x-code:key2, only x-code:key2 takes effect.
   Rule Condition	Do not use conditions	Rule conditions can identify parameters in a request to determine whether a configuration takes effect on the request. Do not use conditions Select the configured rule conditions in Rules Engine. For more information, see Rules engine.

   Parameters of the Delete operation

   

   Parameter	Example	Description
   Operation	Delete	This operation deletes all response headers that match the values of the Response Header and Header Name parameters. Duplicate response headers are also deleted.
   Response Header	Custom Response Header	You can select a preset header or select Custom Response Header from the Response Header drop-down list to specify a response header.
   Header Name	x-code	The name of the custom response header is x-code.
   Rule Condition	Do not use conditions	Rule conditions can identify parameters in a request to determine whether a configuration takes effect on the request. Do not use conditions Select the configured rule conditions in Rules Engine. For more information, see Rules engine.

   Parameters of the Change operation

   

   Parameter	Example	Description
   Operation	Change	You can perform the Change operation only if no duplicate response headers exist.
   Response Header	Custom Response Header	You can select a preset header or select Custom Response Header from the Response Header drop-down list to specify a response header.
   Header Name	x-code	The name of the custom response header is x-code.
   Change Value To	key1,key3	You can specify multiple values for a response header. Separate the values with commas (,).
   Rule Condition		Rule conditions can identify parameters in a request to determine whether a configuration takes effect on the request. Do not use conditions Select the configured rule conditions in Rules Engine. For more information, see Rules engine.

   Parameters of the Replace operation

   

   Parameter	Example	Description
   Operation	Replace	You can perform the Replace operation only if no duplicate response headers exist.
   Response Header	Custom Response Header	You can select a preset header or select Custom Response Header from the Response Header drop-down list to specify a response header.
   Header Name	x-code	The name of the custom response header is x-code.
   Find	key	You can search for the value that you want to replace by using regular expressions.
   Replace With	abc	You can replace matching values by using regular expressions.
   Match	Match All	Match All: All matching values are replaced. For example, if you use a regular expression to replace all strings of "key" in x-code:key1,key2,key3 with abc, the key-value pair is changed to x-code:abc1,abc2,abc3. Match the First Only: Only the first matching value is replaced. For example, if you use a regular expression to replace the first string of "key" in x-code:key1,key2,key3 with abc, the key-value pair is changed to x-code:abc1,key2,key3.
   Rule Condition		Rule conditions can identify parameters in a request to determine whether a configuration takes effect on the request. Do not use conditions Select the configured rule conditions in Rules Engine. For more information, see Rules engine.

8. Click OK.

Default preset response headers

By default, Alibaba Cloud CDN provides the following HTTP response headers: Cache-Control, Content-Type, Expires, and Last-Modified. These response headers are important components of the HTTP protocol that are used to control the cache, define the content type, specify the cache expiration time, and record the last modified time of a resource.

Examples

FAQ