Setting and retrieving properties and metadata for Blob service resources
Containers and blobs support custom metadata, represented as HTTP headers. Metadata headers can be set on a request that creates a new container or blob resource, or on a request that explicitly creates a property on an existing resource.
This topic contains the following subtopics:
Standard HTTP Properties for Containers and Blobs
Blobs also support tags, a special type of custom metadata that is automatically indexed by the Blob service. For more information, see Manage and find data on Azure Blob Storage with Blob Index.
Metadata Header Format
Metadata headers are name/value pairs. The format for the header is:
x-ms-meta-name:string-value
Beginning with version 2009-09-19, metadata names must adhere to the naming rules for C# identifiers.
Names are case-insensitive. Note that metadata names preserve the case with which they were created, but are case-insensitive when set or read. If two or more metadata headers with the same name are submitted for a resource, the Blob service returns status code 400 (Bad Request).
The metadata consists of name/value pairs. The total size of all metadata pairs can be up to 8KB in size.
Metadata name/value pairs are valid HTTP headers, and so they adhere to all restrictions governing HTTP headers.
Operations on Metadata
Metadata on a blob or container resource can be retrieved or set directly, without returning or altering the content of the resource.
Note that metadata values can only be read or written in full; partial updates are not supported. Setting metadata on a resource overwrites any existing metadata values for that resource.
Retrieving Properties and Metadata
The GET and HEAD operations both retrieve metadata headers for the specified container or blob. The HEAD operation returns headers only; it does not return a response body.
The URI syntax for retrieving metadata headers on a container is as follows:
GET/HEAD https://myaccount.blob.core.windows.net/mycontainer?restype=container
The URI syntax for retrieving metadata headers on a blob is as follows:
GET/HEAD https://myaccount.blob.core.windows.net/mycontainer/myblob?comp=metadata
Setting Metadata Headers
The PUT operation sets metadata headers on the specified container or blob, overwriting any existing metadata on the resource. Calling PUT without any headers on the request clears all existing metadata on the resource.
The URI syntax for setting metadata headers on a container is as follows:
PUT https://myaccount.blob.core.windows.net/mycontainer?comp=metadata?restype=container
The URI syntax for setting metadata headers on a blob is as follows:
PUT https://myaccount.blob.core.windows.net/mycontainer/myblob?comp=metadata
Standard HTTP Properties for Containers and Blobs
Containers and blobs also support certain standard HTTP properties. Properties and metadata are both represented as standard HTTP headers; the difference between them is in the naming of the headers. Metadata headers are named with the header prefix x-ms-meta- and a custom name. Property headers use standard HTTP header names, as specified in the Header Field Definitions section 14 of the HTTP/1.1 protocol specification.
The standard HTTP headers supported on containers include:
ETagLast-Modified
The standard HTTP headers supported on blobs include:
ETagLast-ModifiedContent-LengthContent-TypeContent-MD5Content-EncodingContent-LanguageCache-ControlOriginRange
See Also
Create Container
Get Container Properties
Set Container Metadata
Put Blob
Copy Blob
Get Blob Properties
Get Blob Metadata
Set Blob Metadata
Blob Service Concepts
Manage and find data on Azure Blob Storage with Blob Index