Custom Headers

Feature Overview
An HTTP header (metadata header) of an object is a string sent by the server over HTTP before it sends HTML data to the browser. By modifying HTTP headers (metadata headers), you can modify how the webpage responds as well as certain configurations, such as caching time. Modifying an object's HTTP headers does not modify the object itself.
Note: 
For objects of ARCHIVE and DEEP ARCHIVE, custom headers can only be set during upload. Setting custom headers for objects that have already been uploaded is not supported.
How It Works
1. Log in to the COS console.
2. Click Bucket List on the left sidebar.
3. Locate the bucket where the object resides and click the bucket name.
4. Click File List on the left sidebar.
5. Locate the object for which a header is to be customized and click More > Custom Header in the operation column on the right. To customize headers for multiple objects, select multiple objects and click More Actions > Custom Header on the top.
6. In the pop-up window, select the parameter type of the metadata header to be set, enter the metadata value, and click OK.
COS provides the following six types of object HTTP headers for configuration:
HTTP Header
Description
Example
Content-Type
MIME information of the file
image/jpeg
Cache-Control
File caching mechanism
no-cache: Indicates that cache cannot be used directly, but whether the object has been updated must be verified first with the server. If the object has been updated, it indicates that the cache is expired, and the object must be re-downloaded from the server; if the object has not been updated, the cache is not expired, and the local cache will be used.
max-age=200: Indicates the relative expiration time of the cached content, in seconds.
Content-Disposition
Extension of MIME protocol
inline: Directly previews the content of the file.
attachment: Downloads to the specified path in the browser with the original filename.
attachment; filename="FileName": You should download it to the specified path in the browser with a custom filename. FileName defines the name of the file after download, for example, example.jpg. If the attachment name is in Chinese, it needs to be URL encoded, for example, attachment; filename* = UTF-8' '%E4%B8%AD%E6%96%87.txt
Content-Encoding
File encoding format
gzip
Note: If the Content-Encoding in the header has been modified as gzip, but the file has not been compressed with gzip, a decoding error will occur.
Expires
Expiration date of the cache
Wed, 21 Oct 2015 07:28:00 GMT
x-cos-meta-[custom suffix]
User-defined content
x-cos-meta-via: homepage
Note: Header names support only hyphens (-), digits, and English letters (a-z). Uppercase letters in English will be converted to lowercase letters; other characters, including underscores (_), are not supported.
License request example
Assume that a bucket named "examplebucket-1250000000" was created under account APPID 1250000000, and an object "exampleobject.txt" was uploaded to the bucket's root directory.
Non-custom HTTP header of objects
The sample below shows the headers returned for a request to download this object through a browser or client if no custom HTTP headers are specified.
Request
GET /exampleobject.txt HTTP/1.1
Host: examplebucket-1250000000.cos.ap-beijing.myqcloud.com
Date: Fri, 10 Apr 2020 09:35:16 GMT
Authorization: q-sign-algorithm=sha1&q-ak=AKID8A0fBVtYFrNm02oY1g1JQQF0c3JO****&q-sign-time=1586511316;1586518516&q-key-time=1586511316;1586518516&q-header-list=date;host&q-url-param-list=&q-signature=1bd1898e241fb978df336dc68aaef4c0acae****
Connection: close
Response
HTTP/1.1 200 OK
Content-Type: text/plain
Access-Control-Allow-Origin: *
Last-Modified: Fri, 10 Apr 2020 09:35:05 GMT 
Custom HTTP header of objects
Refer to directions to add the following custom header configuration:
Parameter
Value
Content-Type
image/jpeg
Cache-Control
no-cache
Content-Disposition
attachment; filename* = UTF-8' '%E4%B8%AD%E6%96%87.jpeg
x-cos-meta-md5
1234
then the headers returned for new requests will be as follows:
Request
GET /exampleobject.txt HTTP/1.1
Host: examplebucket-1250000000.cos.ap-beijing.myqcloud.com
Date: Fri, 10 Apr 2020 09:35:16 GMT
Authorization: q-sign-algorithm=sha1&q-ak=AKID8A0fBVtYFrNm02oY1g1JQQF0c3JO****&q-sign-time=1586511316;1586518516&q-key-time=1586511316;1586518516&q-header-list=date;host&q-url-param-list=&q-signature=1bd1898e241fb978df336dc68aaef4c0acae****
Connection: close
Response
HTTP/1.1 200 OK
Cache-Control: no-cache
Content-Type: image/jpeg
Content-Disposition: attachment; filename* = UTF-8' '%E4%B8%AD%E6%96%87.jpeg
x-cos-meta-md5: 1234
Access-Control-Allow-Origin: *
Last-Modified: Fri, 10 Apr 2020 09:35:05 GMT 
It can be seen that when custom headers are used, the response format of the page can be changed.

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HTTP Header	Description	Example
Content-Type	MIME information of the file	image/jpeg
Cache-Control	File caching mechanism	no-cache: Indicates that cache cannot be used directly, but whether the object has been updated must be verified first with the server. If the object has been updated, it indicates that the cache is expired, and the object must be re-downloaded from the server; if the object has not been updated, the cache is not expired, and the local cache will be used. max-age=200: Indicates the relative expiration time of the cached content, in seconds.
Content-Disposition	Extension of MIME protocol	inline: Directly previews the content of the file. attachment: Downloads to the specified path in the browser with the original filename. attachment; filename="FileName": You should download it to the specified path in the browser with a custom filename. FileName defines the name of the file after download, for example, example.jpg. If the attachment name is in Chinese, it needs to be URL encoded, for example, `attachment; filename* = UTF-8' '%E4%B8%AD%E6%96%87.txt`
Content-Encoding	File encoding format	gzip Note: If the Content-Encoding in the header has been modified as gzip, but the file has not been compressed with gzip, a decoding error will occur.
Expires	Expiration date of the cache	Wed, 21 Oct 2015 07:28:00 GMT
x-cos-meta-[custom suffix]	User-defined content	x-cos-meta-via: homepage Note: Header names support only hyphens (-), digits, and English letters (a-z). Uppercase letters in English will be converted to lowercase letters; other characters, including underscores (_), are not supported.

Parameter	Value
Content-Type	image/jpeg
Cache-Control	no-cache
Content-Disposition	attachment; filename* = UTF-8' '%E4%B8%AD%E6%96%87.jpeg
x-cos-meta-md5	1234

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Feature Overview

How It Works

License request example

Non-custom HTTP header of objects

Request

Response

Custom HTTP header of objects

Request

Response