TrailSiftWhat private browsing does
In Safari, Chrome, Firefox and the rest, a private window doesn't add pages to your history, doesn't keep cookies or site data after you close it, and doesn't fill in searches or forms from it later. That's useful, and it's all it promises.
What it doesn't touch
Files you download
A file downloaded in a private window is an ordinary file in your Downloads folder, and it stays there until you delete it. Depending on the browser, macOS can also note where it came from: Get Info shows it as Where from, and macOS keeps its own log of downloads, apart from any browser. Clearing history in the browser leaves both alone.
What you open and preview
Open that file, and it can appear in Recent Items and the app's Open Recent list. Press Space to look at it, and Quick Look may keep a small thumbnail in a hidden cache, which can outlast the file itself.
The networks you join
Your Mac remembers every Wi-Fi network it has joined, by name, and many network names are the names of places: a hotel, a café, an office, a friend's home.
Everyone between you and the site
Your internet provider, the network you're on (at work or school, say) and the sites themselves still see your visits. If you sign in to an account in a private window, that account can keep its own history of what you did.
What you type
The keyboard learns words you type to improve its suggestions, and a word you teach the spell checker stays in its list. Those lists belong to macOS, not the browser.
Check your own Mac
Every Mac is different, because it depends on the browsers and apps you use. TrailSift's free audit reads each of these places, and many more, without changing anything, and tells you what's there, how much and from when. Nothing it finds leaves your Mac. If you'd like to clear any of it, Pro does that after showing you exactly what will go, or the app tells you how to do it yourself.
For the full list of places, with sources, see What TrailSift checks.
Updated 13 October 2026. More guides: all TrailSift guides.