X-Version

The HTTP X-Version response header is an unofficial header exposing the version of the application, framework, or CMS generating the response.

Table of Contents

Usage

Application servers, CMS platforms, and custom web applications include X-Version to communicate the version of the software producing the response. The header is used internally for deployment tracking, debugging, and verifying which release is active in a given environment.

Values vary by platform. Semantic version strings like 1.2.3 are common. Build identifiers, commit hashes, and release tags also appear depending on how the deployment pipeline is configured. The format is not standardized and reflects whatever versioning scheme the development team uses.

In development and staging environments, X-Version helps confirm which release is running after a deployment. In production, the header is typically removed. Exposing application version information gives attackers a precise target when known vulnerabilities exist for specific releases. Security-conscious deployments strip this header at the reverse proxy or CDN layer before responses reach clients.

X-Version serves a similar purpose to X-Powered-By, which identifies the runtime or framework, and X-Generator, naming the tool or CMS generating the page. X-Version specifically targets the application's own version number rather than the underlying technology.

Note

The X- prefix for non-standard headers is deprecated per RFC 6648.

Values

The value is an opaque version string defined by the application. Common formats include:

  • 1.2.3: semantic version with major, minor, and patch components
  • 2.0.0-beta.4: pre-release semantic version
  • build-9f3a2c1: short commit hash or build identifier
  • v4.12: version tag with a v prefix

Example

A web application running semantic versioning sends the current release number. An operator checking the response headers after deployment confirms the correct version is active.

X-Version: 1.2.3

A CMS using build identifiers instead of version numbers sends a commit hash or pipeline build number.

X-Version: build-9f3a2c1

A staging environment exposes additional detail with a pre-release label alongside other version-related headers.

X-Version: 2.0.0-beta.4
X-Powered-By: Express

Takeaway

The X-Version header communicates the application's release version for deployment tracking and debugging. The header is generally removed in production environments to avoid exposing version details aiding attackers in targeting known vulnerabilities.

See also

Last updated: March 6, 2026