X-ContextId

On shared hosting platforms, routing a response back to the correct account requires an internal identifier. The X-ContextId unofficial response header exposes this opaque hosting context identifier in HTTP responses.

Usage

Shared hosting environments route requests from many different accounts through common infrastructure. The X-ContextId header provides a short identifier associating a response with the specific hosting context (the account, site, or configuration slot) generating the response.

The value is an opaque alphanumeric string, often including a slash as a separator between components. The format is specific to each hosting platform and carries no standardized meaning across providers. External clients receive the header as part of the response, but the value is intended for internal platform diagnostics rather than consumption by browsers or API clients.

The header allows hosting platform engineers to correlate log entries with the specific account context when troubleshooting shared infrastructure issues. Its role is similar to X-Request-Id, though X-ContextId identifies the hosting context rather than a specific request.

Values

Opaque context identifier

The header value is a short alphanumeric string. Some platforms include a slash separating two components, where the first part identifies a region or cluster and the second part identifies the specific context within the region or cluster.

Example

A response from a shared hosting environment includes a context identifier consisting of alphanumeric characters separated by a slash. The first segment indicates a broader grouping and the second identifies the specific account or context slot.

X-ContextId: mLtZi0va/HaKz4Ve2

Different accounts on the same platform produce different identifiers. The format stays consistent while the values change with each account.

X-ContextId: jdlCbfFq/Jlddg2qM

See also

• X-Request-Id
• HTTP headers