What you are installing. Hover any element on any page and read its
exact size, padding, margin and font. Pin two things and get the measured
distance between them. Audit a whole page for contrast failures, off-grid
spacing and duplicate ids — every finding marked where it is, not just
listed. Then copy one structured report to paste into an AI chat.
All of it reads the rendered page, so the numbers are
what the browser actually did — not what the CSS intended.
Step 1 of 4 is already done — you extracted the ZIP,
which is why this page is open. Three left. This page carries the whole
extension inside itself and needs no command prompt, so it works even where
administrators disable cmd; the browser reserves two clicks for you.
Step 2 — write the files.
Press the button and choose Documents\debug-overlay — create
it in the picker if it does not exist. Any permanent folder works; that one
is suggested so you do not have to decide. Not Downloads and not a
temp folder: Chrome re-reads this folder every time it starts, so if it
disappears, the extension does. Already installed? Pick your existing install
folder — the exact folder you loaded unpacked — and this page updates it
in place.
Step 3 — open the extensions page.
A web page is not allowed to open it for you. Copy the address and paste it
into the address bar:
chrome://extensions(Edge: edge://extensions)
Step 4 — the two clicks the browser requires from a human.
On that page: switch ON Developer mode (top-right), press
Load unpacked, and select the folder from Step 2. Why Developer mode: Chrome requires it for any
extension not installed from its store — this is the browser's rule, not
ours. Leave it on. Switching it off later disables Debug Overlay,
and the reason is not obvious when it happens. Updated an existing folder in Step 2? Then just press
↻ Reload on Debug Overlay instead — it is already loaded.
Then open any website and press Alt+Shift+D.
Optional, once — one-press future updates.
Extension's Details → Extension options → Choose install folder… →
select the same folder → Allow. From then on updates are a single press
inside the overlay.