Tab-switch detection test
Is this tab
being watched?
This page detects tab switches the way a tracking site would: it listens for visibilitychange and window blur, polls document.hasFocus(), and hashes your canvas, WebGL and audio output. Switch away and come back to see what it caught, then try again with Focus Spoofer on.
visibilityState
…
document.hasFocus()
…
Canvas hash
…
WebGL hash
…
Audio hash
…
Event log
Focus test
- Turn on Focus Spoofer for this tab from the toolbar.
- Switch to another tab, or minimize the window, for a few seconds.
- Come back. No blur or visibility entries in the log means it's working.
Fingerprint test
- With the extension off, reload a few times. The three hashes stay the same.
- Turn it on and reload again. The hashes now change on every load.
- Turned fingerprint randomization off in Settings? Then they stay the same, by design.
What each check means
| Check | Without protection, after a tab switch | With Focus Spoofer |
|---|---|---|
visibilitychange / document.hidden | Log shows Visibility: hidden, then visible | No entries; hidden stays false |
Window blur / focus | Log shows Window blurred, then focused | No entries |
document.hasFocus() | false while you're away | Always true |
| Canvas, WebGL, audio hash | Same value on every reload (a stable fingerprint) | Changes on every reload, unless fingerprint randomization is off in Settings |
Other signals exist that no browser extension can hide from every site, such as server-side activity timing. See the FAQ for what Focus Spoofer does and doesn't cover.