X-MS-Request-Id
The HTTP X-MS-Request-Id response header is an unofficial HTTP header containing a unique identifier assigned by Microsoft Azure services to each request.
Note
The "X-" naming convention for HTTP headers, "X" referring to "experimental", has been deprecated and needs to be transitioned to the formal naming convention for HTTP headers.
Usage
Azure services such as Blob Storage, Cosmos DB, Azure Functions, and Microsoft Entra ID (formerly Azure Active Directory) attach a unique request identifier to every response. This identifier appears in the X-MS-Request-Id header and in Azure server-side diagnostic logs, creating a direct link between a specific client response and the internal processing record.
The value follows the GUID format (a 128-bit identifier formatted as five groups of hexadecimal digits separated by hyphens). When a storage or API request fails or behaves unexpectedly, including this identifier in an Azure support ticket allows engineers to locate the exact request in diagnostic logs and trace the full processing path. The header works alongside X-Azure-Ref, which serves a similar correlation role for Azure Front Door and Azure CDN. The X-Request-Id header fills the same general purpose for non-Azure systems, while Request-Context carries Application Insights correlation data for distributed tracing.
Values
GUID string
The value is a GUID (Globally Unique Identifier) in the
standard 8-4-4-4-12 hexadecimal format. Each request
generates a distinct identifier. The GUID is assigned
server-side by the Azure service handling the request and
is not influenced by any client-supplied headers.
Example
A response from Azure Blob Storage includes a GUID
identifying the specific storage operation. The value
9463a893-b01e-00c1-3720-70cc08000000 is unique to this
request and appears in the corresponding Azure Storage
Analytics log entry.
X-MS-Request-Id: 9463a893-b01e-00c1-3720-70cc08000000
A request to Microsoft Entra ID returns a different GUID format with the same structure. Providing this value when filing a support ticket enables Microsoft engineers to trace Authentication and token issuance steps.
X-MS-Request-Id: e6905c71-5142-4f5c-b3db-818890240900
Azure responses often include multiple correlation headers together. The X-MS-Request-Id identifies the specific service-level operation, while X-Azure-Ref tracks the CDN or Front Door routing path.
X-MS-Request-Id: 69c49ab2-001e-003d-035b-69b062000000
X-Azure-Ref: 20260219T072807Z-r1f8558ffbc6zxmzhC1BY1zg6n00000008u000000000a7cs
Takeaway
The X-MS-Request-Id header provides a unique GUID for each request processed by Azure services, used for diagnostic log correlation and support ticket troubleshooting.