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Put Blob

Updated: January 31, 2014

The Put Blob operation creates a new block blob or page blob, or updates the content of an existing block blob.

Updating an existing block blob overwrites any existing metadata on the blob. Partial updates are not supported with Put Blob; the content of the existing blob is overwritten with the content of the new blob. To perform a partial update of the content of a block blob, use the Put Block List operation.

Note that calling Put Blob to create a page blob only initializes the blob. To add content to a page blob, call the Put Page operation.

The Put Blob request may be constructed as follows. HTTPS is recommended. Replace myaccount with the name of your storage account:


  PUT Method Request URI HTTP Version


When making a request against the emulated storage service, specify the emulator hostname and Blob service port as, followed by the emulated storage account name:


  PUT Method Request URI HTTP Version


Note that the storage emulator only supports blob sizes up to 2 GB.

For more information, see Using the Azure Storage Emulator for Development and Testing.

The following additional parameters may be specified on the request URI.


Parameter Description


Optional. The timeout parameter is expressed in seconds. For more information, see Setting Timeouts for Blob Service Operations.

The following table describes required and optional request headers for operations on both block blobs and page blobs.


Request header Description


Required. Specifies the authentication scheme, account name, and signature. For more information, see Authentication for the Azure Storage Services.

Date or x-ms-date

Required. Specifies the Coordinated Universal Time (UTC) for the request. For more information, see Authentication for the Azure Storage Services.


Required for all authenticated requests. Specifies the version of the operation to use for this request. For more information, see Versioning for the Azure Storage Services.


Required. The length of the request.

For a page blob, the value of this header must be set to zero, as Put Blob is used only to initialize the page blob. The page blob's size is specified in the x-ms-blob-content-length header. All content must be written to a page blob by calling Put Page.


Optional. The MIME content type of the blob. The default type is application/octet-stream.


Optional. Specifies which content encodings have been applied to the blob. This value is returned to the client when the Get Blob operation is performed on the blob resource. The client can use this value when returned to decode the blob content.


Optional. Specifies the natural languages used by this resource.


Optional. An MD5 hash of the blob content. This hash is used to verify the integrity of the blob during transport. When this header is specified, the storage service checks the hash that has arrived with the one that was sent. If the two hashes do not match, the operation will fail with error code 400 (Bad Request).

When omitted in version 2012-02-12 and later, the Blob service generates an MD5 hash.

Results from Get Blob, Get Blob Properties, and List Blobs include the MD5 hash.


Optional. The Blob service stores this value but does not use or modify it.


Optional. Set the blob’s content type.


Optional. Set the blob’s content encoding.


Optional. Set the blob's content language.


Optional. Set the blob’s MD5 hash.


Optional. Sets the blob's cache control.

x-ms-blob-type:<BlockBlob | PageBlob>

Required. Specifies the type of blob to create: block blob or page blob.


Optional. Name-value pairs associated with the blob as metadata.

Note that beginning with version 2009-09-19, metadata names must adhere to the naming rules for C# identifiers.


Required if the blob has an active lease. To perform this operation on a blob with an active lease, specify the valid lease ID for this header.


Optional. Sets the blob’s Content-Disposition header. Available for versions 2013-08-15 and later.

The Content-Disposition response header field conveys additional information about how to process the response payload, and also can be used to attach additional metadata. For example, if set to attachment, it indicates that the user-agent should not display the response, but instead show a Save As dialog with a filename other than the blob name specified.

The response from the Get Blob and Get Blob Properties operations includes the content-disposition header.


Optional. Specifies the origin from which the request is issued. The presence of this header results in cross-origin resource sharing headers on the response. See Cross-Origin Resource Sharing (CORS) Support for the Azure Storage Services for details.


Optional. Provides a client-generated, opaque value with a 1 KB character limit that is recorded in the analytics logs when storage analytics logging is enabled. Using this header is highly recommended for correlating client-side activities with requests received by the server. For more information, see About Storage Analytics Logging and Windows Azure Logging: Using Logs to Track Storage Requests.

This operation also supports the use of conditional headers to write the blob only if a specified condition is met. For more information, see Specifying Conditional Headers for Blob Service Operations.

The following table describes request headers applicable only for operations on page blobs.


Request header Description

x-ms-blob-content-length: bytes

Required for page blobs. This header specifies the maximum size for the page blob, up to 1 TB. The page blob size must be aligned to a 512-byte boundary.

If this header is specified for a block blob, the Blob service returns status code 400 (Bad Request).

x-ms-blob-sequence-number: <num>

Optional. Set for page blobs only. The sequence number is a user-controlled value that you can use to track requests. The value of the sequence number must be between 0 and 2^63 - 1.The default value is 0.

For a block blob, the request body contains the content of the blob.

For a page blob, the request body is empty.

The following example shows a request to create a block blob:

Request Syntax:

Request Headers:
x-ms-version: 2013-08-15
x-ms-date: Wed, 23 Oct 2013 22:33:355 GMT
Content-Type: text/plain; charset=UTF-8
x-ms-blob-content-disposition: attachment; filename="fname.ext"
x-ms-blob-type: BlockBlob
x-ms-meta-m1: v1
x-ms-meta-m2: v2
Authorization: SharedKey myaccount:YhuFJjN4fAR8/AmBrqBz7MG2uFinQ4rkh4dscbj598g=
Content-Length: 11

Request Body:
hello world

This sample request creates a page blob and specifies its maximum size as 1024 bytes. Note that you must call Put Page to add content to a page blob:

Request Syntax:

Request Headers:
x-ms-version: 2013-08-15
x-ms-date: Wed, 23 Oct 2013 22:41:55 GMT
Content-Type: text/plain; charset=UTF-8
x-ms-blob-type: PageBlob
x-ms-blob-content-length: 1024
x-ms-blob-sequence-number: 0
Authorization: SharedKey 
Vary: Origin
Content-Length: 0

The response includes an HTTP status code and a set of response headers.

A successful operation returns status code 201 (Created).

For information about status codes, see Status and Error Codes.

The response for this operation includes the following headers. The response can also include additional standard HTTP headers. All standard headers conform to the HTTP/1.1 protocol specification.


Response header Description


The ETag contains a value that the client can use to perform conditional PUT operations by using the If-Match request header. If the request version is 2011-08-18 or newer, the ETag value will be in quotes.


The date/time that the blob was last modified. The date format follows RFC 1123. For more information, see Representation of Date/Time Values in Headers.

Any write operation on the blob (including updates on the blob's metadata or properties) changes the last modified time of the blob.


This header is returned for a block blob so the client can check the integrity of message content. The Content-MD5 value returned is computed by the Blob service. In version 2012-02-12 and later, this header is returned even when the request does not include Content-MD5 or x-ms-blob-content-md5 headers.


This header uniquely identifies the request that was made and can be used for troubleshooting the request. For more information, see Troubleshooting API Operations.


Indicates the version of the Blob service used to execute the request. This header is returned for requests made against version 2009-09-19 and later.


A UTC date/time value generated by the service that indicates the time at which the response was initiated.


Returned if the request includes an Origin header and CORS is enabled with a matching rule. This header returns the value of the origin request header in case of a match.


Returned if the request includes an Origin header and CORS is enabled with a matching rule. Returns the list of response headers that are to be exposed to the client or issuer of the request.


Returned if the request includes an Origin header and CORS is enabled with a matching rule that does not allow all origins. This header will be set to true.

Response Status:
HTTP/1.1 201 Created

Response Headers:
Transfer-Encoding: chunked
Content-MD5: sQqNsWTgdUEFt6mb5y4/5Q==
Date: Wed, 23 Oct 2013 22:33:35 GMT
ETag: "0x8CB171BA9E94B0B"
Last-Modified: Wed, 23 Oct 2013 22:30:15 GMT
Access-Control-Expose-Headers: Content-MD5
Access-Control-Allow-Credentials: True
Server: Windows-Azure-Blob/1.0 Microsoft-HTTPAPI/2.0

This operation can be called by the account owner and by any client with a shared access signature that has permission to write to this blob or its container.

When you create a blob, you must specify whether it is a block blob or a page blob. Once a blob has been created, the type of the blob cannot be changed unless it is deleted and re-created.

To create a new page blob, first initialize the blob by calling Put Blob and specify its maximum size, up to 1 TB. When creating a page blob, do not include content in the request body. Once the blob has been created, call Put Page to add content to the blob or to modify it.

The maximum upload size for a block blob is 64 MB. If your blob is larger than 64 MB, you must upload it as a set of blocks. For more information, see the Put Block and Put Block List operations. It's not necessary to call Put Blob if you upload the blob as a set of blocks.

If you attempt to upload a block blob that is larger than 64 MB, or a page blob larger than 1 TB, the service returns status code 413 (Request Entity Too Large). The Blob service also returns additional information about the error in the response, including the maximum blob size permitted in bytes.

If you call Put Blob to overwrite an existing blob with the same name, any snapshots associated with the original blob are retained. To remove associated snapshots, call Delete Blob first, then Put Blob to re-create the blob.

A blob has custom properties (set via headers) that you can use to store values associated with standard HTTP headers. These values can subsequently be read by calling Get Blob Properties, or modified by calling Set Blob Properties. The custom property headers and corresponding standard HTTP header are listed in the following table:


HTTP header Custom blob property header











The semantics for setting persisting these property values with the blob as follows:

  • If the client specifies a custom property header, as indicated by the x-ms-blob prefix, this value is stored with the blob.

  • If the client specifies a standard HTTP header, but not the custom property header, the value is stored in the corresponding custom property associated with the blob, and is returned by a call to Get Blob Properties. For example, if the client sets the Content-Type header on the request, that value is stored in the blob's x-ms-blob-content-type property.

  • If the client sets both the standard HTTP header and the corresponding property header on the same request, the PUT request uses the value provided for the standard HTTP header, but the value specified for the custom property header is persisted with the blob and returned by subsequent GET requests.

If the blob has an active lease, the client must specify a valid lease ID on the request in order to overwrite the blob. If the client does not specify a lease ID, or specifies an invalid lease ID, the Blob service returns status code 412 (Precondition Failed). If the client specifies a lease ID but the blob does not have an active lease, the Blob service also returns status code 412 (Precondition Failed). If the client specifies a lease ID on a blob that does not yet exist, the Blob service will return status code 412 (Precondition Failed) for requests made against version 2013-08-15 and later; for prior versions the Blob service will return status code 201 (Created).

If an existing blob with an active lease is overwritten by a Put Blob operation, the lease persists on the updated blob, until it expires or is released.

A Put Blob operation is permitted 10 minutes per MB to complete. If the operation is taking longer than 10 minutes per MB on average, the operation will timeout.

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