The metadata consists of name/value pairs. The total size of all metadata pairs can be up to 8KB in size. More information in the documentation here.
Metadata name/value pairs are valid HTTP headers and should adhere to all restrictions governing HTTP headers. Metadata names must be valid HTTP header names and valid C# identifiers, may contain only ASCII characters, and should be treated as case-insensitive. Base64-encode or URL-encode metadata values containing non-ASCII characters.
The name of your metadata must conform to the naming conventions for C# identifiers. Metadata names maintain the case used when they were created, but are case-insensitive when set or read. If two or more metadata headers using the same name are submitted for a resource, Azure Blob storage returns HTTP error code 400 (Bad Request).
Blob index tags also provide the ability to store arbitrary user-defined key/value attributes alongside an Azure Blob storage resource. While similar to metadata, only blob index tags are automatically indexed and made searchable by the native blob service. Metadata cannot be indexed and queried unless you utilize a separate service such as Azure Search.
To learn more about this feature, see Manage and find data on Azure Blob storage with blob index (preview).
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