Why Chrome says "Page Scanner started debugging this browser"

The bar is Chrome's own notice that an extension is using its debugger. Page Scanner attaches it for the length of one scan, to lay the page out once and take the PDF from that layout, and nothing leaves your machine.

The bar at the top of the window is Chrome's, not Page Scanner's. Chrome shows it whenever an extension attaches its debugger to a tab, and Page Scanner attaches it for one reason: the debugger is the only way an extension can reach Chrome's own print-to-PDF pipeline, which is what makes the PDF's text real text rather than a picture of text. The bar appears when a scan starts and goes away when the scan finishes, a few seconds on an ordinary page and longer on a very large one. Nothing is inspected, and nothing leaves the machine.

What the bar says

Chrome puts one line under the address bar, in a bar of its own, with a Cancel button at the right:

"Page Scanner" started debugging this browser

It is Chrome's wording, and Chrome shows the same line for any extension that uses the debugger, with that extension's name in the quotes. Pressing Cancel detaches the debugger, which ends the scan; scan again when you want the capture.

What the debugger is used for

One attachment, one layout, two outputs. While the debugger is attached, Page Scanner lays the page out once at its full height, then takes two things from that single layout: a screenshot, which is the preview you crop in the editor, and Chrome's print-to-PDF output, which is the file. Because both come from the same layout, the crop you draw on the preview lands exactly on the PDF.

Without the debugger, an extension can only scroll the page a screen at a time and stitch the screenshots together. That gives a picture of the text, not the text. Page Scanner does exactly that as a fallback when the debugger cannot attach, most often because DevTools is already open on the tab, and the editor's toolbar labels that capture Raster so you know which kind you have. Close DevTools and scan again to get a vector capture.

Why it cannot be hidden

The bar is drawn by Chrome for any extension that uses the debugger API, and no extension can suppress it. Page Scanner does not try to, and the settings page has no switch for it. The one thing that turns it off is a command-line switch on Chrome itself, --silent-debugger-extension-api, which exists for automated test setups; Page Scanner does not ask you to use it.

What it does not mean

Chrome's wording says "debugging this browser", and what is happening is narrower than that: the debugger is attached to the one tab you scanned, for the length of that scan, and detached the moment it is done. Page Scanner never runs in the background, never watches pages you have not scanned, and has no access to any other tab. It asks for no host permissions, so it has no standing access to any site.

There is no account, no telemetry and no server. The capture is written to the extension's own storage in your browser so the editor tab can open it, and anything older than 12 hours is deleted the next time the extension starts. The one network path that exists at all is an optional bridge on 127.0.0.1 for a program on your own machine, and it is off until you pair it.

These are the permissions the extension asks for, as the privacy policy lists them:

Permission	Why it is needed
`activeTab`	Grants access to the one tab you scan, at the moment you click the icon, and to nothing else.
`debugger`	Lays the tab out at its full content size and takes the full-page screenshot and the vector PDF from that one layout. This is the capture, and it is the only Chrome API that can produce a real vector PDF of a whole page.
`scripting`	Measures the page's full height, and drives the scroll-and-stitch fallback used when the debugger cannot attach (for example when DevTools is open).
`storage`	Remembers your light/dark theme, your video setting, and the bridge pairing, on this device.
`favicon`	Shows the scanned site's icon in the editor, read from Chrome's local favicon cache. No request leaves the browser.

What the mechanism costs

The limits that come with capturing this way, as the extension's own feature record states them:

Chrome shows its own "started debugging this browser" bar for the length of a scan, and it cannot be suppressed.
With DevTools open on the tab the capture falls back to stitching screenshots, and the editor labels the result Raster.
Only one debugger can attach to a tab at a time.
chrome:// pages, the Chrome Web Store and other extensions' pages cannot be scanned.