## HTTP Header

### User Agent

The User-Agent request-header field contains the Web browser’s signature. This is for:

- tracking requests,
- statistical purposes,
- tracing protocol violations, and
- automated user agent recognition to tailor responses to avoid particular user agent limitations.

User agents should include the User-Agent request-header field with requests. The field can contain multiple product tokens and comments identifying the agent (browser) and any sub-products that form a significant part of the user agent. By convention, the product tokens are listed in order of their significance in identifying the application.

    User-Agent = "User-Agent" ":" 1*(product | comment)

    Example: User-Agent: CERN-LineMode/2.15 libwww/2.17b3

The User-Agent header is included in all HTTP messages initiated by the browser, formatted as specified below for the appropriate IP telephone.