window.devicePixelRatio

[llc0930]

sidebery/src/injections/tab-preview.ts

Lines 126 to 131 in 5c6c794

	function compensateZoom() {
	if (!state.rootEl) return
	if (state.referenceDevicePixelRatio === window.devicePixelRatio) return
	state.compScale = state.referenceDevicePixelRatio / window.devicePixelRatio
	state.rootEl.style.transform = `scale(${state.compScale})`
	}

Firefox reports window.devicePixelRatio as 2 on the General tab and 1 on the Settings tab.
This resulted in me actually always getting a preview window that was 50% of the expected size.

[llc0930]

Looking back, it was indeed about the same time I realized the preview had become smaller.
https://phabricator.services.mozilla.com/D207834

[llc0930]

After turning off anti-fingerprint recognition, the behavior is normal. This discussion is left for people who encounter the same doubts... I decided to give up trying this function and choose anti-fingerprint recognition.