How to check whether an online file tool uploads your files

You can check whether an online file tool uploads your files in about five minutes, without relying on the site's word. Open the tool, watch the browser's Network tab while you run it on a file, then turn off the internet and run it again. If the file never leaves the device, no request in the Network tab carries it, and the tool still works offline. The privacy page states what the owner intends. The first two checks show what actually happens.

Check 1: watch the Network tab

The browser's developer tools record every request a page makes.

1. Open the tool in Chrome, Edge or Firefox on a computer. Press F12, or Ctrl+Shift+I on Windows and Linux, or Cmd+Option+I on a Mac, then open the Network tab.
2. Tick Preserve log (Firefox calls it Persist Logs), so requests survive a page change, and press the clear icon to empty the list.
3. Add your file, run the tool and wait for the result.
4. Read the list. An upload appears as a request with a body, usually a POST, and its size is close to the size of your file. Click the request and look at its payload or form data. A download is different: it is a response, and its size is what you receive.

If a request carries your file, the tool uploads it. If you see only requests for the page, its scripts, fonts and images, the file stayed on your device. Sort the list by size to find large requests quickly.

Some tools download something on the first run. Remove background fetches its AI model then, which shows as a large download with no file in its request. That is a download to your device, not an upload.

Check 2: go offline after loading

1. Load the tool and let the page finish loading.
2. If the tool needs a download on its first run, run it once while online so the download completes.
3. Turn on airplane mode, or disconnect from the network.
4. Run the tool again on a different file.

If the result appears, the job needed no server. If the tool stops with a network error, something in the job depends on a server. Repeat the test once, so that a fault unrelated to the network does not mislead you.

Check 3: read the privacy page with care

Privacy pages state intent, so look for specific claims:

• Does it say files are processed in your browser or on your device, or does it say uploads are stored or kept for a period? A retention period means a server holds your file.
• Does it name the companies that receive file content? Analytics that counts page views is different from a service that receives files.
• Is there a date near the top? An undated policy is hard to hold a site to.

Use the privacy page as a starting point. The first two checks test what it says.

Why in-browser processing exists

Modern browsers can run image, PDF and text code on the device. The page does the work in its own memory, using built-in browser features and JavaScript libraries. Because nothing has to go to a server, the site needs no storage for your files, which is why such tools can be free and can keep working offline. The cost falls on your device, so a very large file or an old phone can be slow.

It also means the code the site serves is what you should trust, not a sentence about it. A page can run only the code it sends, so the Network tab and the offline test are the evidence.

How the fixmint tools fit

fixmint's tools run in the browser, and the tool pages and privacy page say so. You can test them with these checks. Open the Network tab and run compress an image or merge PDFs, or go offline and run remove a background a second time, after its model has downloaded. fixmint uses Google Analytics 4 to count page views and which tool is used, and its privacy page says file names and content are never sent. Those analytics requests will show in the Network tab, but they should not carry your file. This article describes checks you can run yourself. It is not a certificate or an independent audit.

Edge cases

• Upload buttons. A tool may upload only when you press a particular button, such as Share, Save online or Convert in the cloud. Check each action, not just the first.
• Browser extensions. Extensions with permission to read pages can see what you open. Test in a clean profile, or with extensions off, when the file is sensitive.
• Phones. Most phone browsers do not offer a simple Network tab, so run the first two checks on a computer. The offline check works on a phone too.
• Shared machines. On a shared computer, clear the downloads folder and history after the job, since the file may remain there.