What is the User-Agent header?

User-Agent is a request header that tells a server about the sending software. It may contain browser, OS, and compatibility information.

What can it tell you?

Servers may use it as a clue for compatibility behavior. The string can be modified and does not reliably prove a product or OS.

How NetKarte shows it

Read User-Agent under Client headers in the HTTP information card. No input is needed: this is the value received by the NetKarte server for this request. For comparison, read User-Agent in the Browser card of the same diagnosis. That value comes from a browser API, so the collection paths differ.

Notes

Long values include identifiers retained for compatibility. Do not interpret every named token as a product or feature actually in use.

When the browser card differs

The HTTP value reached the server; the browser value was available to JavaScript. Extensions, compatibility settings, intermediaries, or different collection times may need investigation. A mismatch alone is not proof of tampering.

Reload the same tab and compare both values. Use the browser's own About screen to confirm its product and version. You do not need to disable all privacy protections.

Why several product names appear

Tokens such as Mozilla/5.0 and Safari can exist for compatibility. They do not mean that several browsers are running simultaneously. Identifying a product from a single token is unreliable.

The displayed header cannot authenticate a visitor or establish that a request is human. Nor does this one request prove that every request to other sites carries the same value.