| Header | Value | What it does |
|---|
Analysing works offline
Pasting a message parses it entirely in this page. Nothing is uploaded, and no request is made. Raw HTTP/1.1, HTTP/2 pseudo-header dumps, DevTools' copied header view, curl commands and HAR entries all normalise to the same view.
Sending needs the extension
A web page cannot issue a cross-origin request and read the response — the browser blocks it unless the target site opts in with CORS. That rule is what stops any page you visit from reading your logged-in session elsewhere, so there is no way around it from inside the page.
The optional HelpyTools extension does the request from its own background worker, which holds the permission the page lacks. It still runs on your machine; nothing reaches a HelpyTools server. Without the extension installed, the Send button stays hidden and everything else works as normal.
Headers your browser controls
Even when sending through the extension, some headers are reserved by the browser and cannot be set from script — Host, Connection and Content-Length among them, and Chrome drops User-Agent from this kind of request. Any header you set that the browser overrode is marked browser-controlled in the table above, so what you see is what actually went out.