A physics engine, and a verification tool enforced on top of it. PhysWall inverts a closed, published, non-linear physical law at a single measurement point — and refuses when the inverse is not unique. Seven laws, one engine, and the same refusal in all of them.
The extension collects nothing. This page says so in the detail the Chrome Web Store asks for, and in the detail a reader can check against the files themselves.
One purpose: to mark the claims in an AI chat answer that cannot be checked as written, and to say what is missing. That is two things wearing one purpose, and both are the same act of reading: a number is checked against a published law and refused when it breaks one; a word that states a count without giving it — “most”, “usually”, “significantly” — is marked only when no count nearby supplies it. Everything else on this page follows from that.
The second kind never says the sentence is wrong. It says a number was claimed and not given, which is a fact about the sentence rather than a judgement about the world, and the mark is drawn in grey rather than orange to say so before it is opened.
Two things, both already on the screen in front of you: the answer, and the message you sent. It reads your message so that it can tell you what the question leaves out — ask what efficiency a combined cycle reaches, and it says that the answer cannot be checked without the temperatures. Both are read in the page, as they are drawn. Neither is stored, and neither is sent anywhere.
Nothing. The extension contains no network code of any
kind: no fetch, no request, no server of ours or anyone else's. You
can confirm that by searching the files for the word
fetch — there are none.
Nothing is written to disk. The marks exist in the page you are reading and disappear when you close it.
Access to five sites — ChatGPT, Claude, Gemini, Mistral and Meta AI — so that it can read the text of an answer, and of the message you sent, and mark them. Chrome shows you those five when you install it. They are written as six entries, because Meta AI answers on two addresses; the store listing names all six for that reason, and it is the same five sites. It asks for no other permission: no tabs, no history, no storage, no downloads.
No marked number links anywhere. Every one of the twenty-eight subjects is worked out in the page you are reading, or says what is missing and stops. The only links the extension ever offers come from three phrases — “possible causes”, “margin of error”, “priced in” — each of which names a question one of the tools on this site is built for, and each offered at most once in an answer. Opening that link is your choice, the tool opens empty in a new tab, and you type the numbers yourself. Nothing travels with the link. A word marked for a missing count never links anywhere — there is nothing to work out.
If a version ever collects or sends anything, this page will say so before that version is released, and the Chrome Web Store listing will say so too. A privacy page that disagrees with the code is worse than none.
Support: service@physwall.com
The extension, and how to read it