Does this website upload my files? How to check

The claim and the check

Plenty of file tools now say "your files never leave your browser". Some mean it. The good news is that you do not need to trust any of them, including this site: every browser has a panel that lists each request a page makes, and an uploaded file is a request. Here is how to read it.

Step 1: open the network panel

Open the tool's page. Press F12 on Windows or Linux, Cmd-Option-I on a Mac, or right-click the page and choose Inspect. A panel opens; pick the tab labelled Network. Reload the page so the list starts fresh. You will see the page's own files load: HTML, scripts, styles, maybe a font, maybe a large file for a decoder. That is the site delivering its program to you, and it is expected.

Step 2: clear the list, then add a file

Click the clear button (a circle with a line through it) so the list is empty. Now drop your file onto the tool and run it. Watch the list.

Step 3: read what appears

Three outcomes cover almost every tool:

• An upload. A row appears with method POST or PUT, often to a path like /upload or /api/convert, and its size (the Size column, or the request's Payload tab) matches your file. The file left your computer. Everything the site says about deletion applies from here.
• Nothing, or only small pings. The list stays empty, or shows a few requests of under a couple of kilobytes to an analytics host. Your file did not leave. A row can also appear for a decoder or library the tool fetches on demand; that is a GET with no payload, and you can confirm it by clicking it: the request has no body.
• Chunks. Some uploaders split large files into many POST requests of a few megabytes each. The pattern is the same: outgoing requests with bodies that add up to your file.

Step 4: the airplane-mode test

For a second opinion that needs no panel at all: after one visit and a short wait, switch on airplane mode or unplug the network and run it. (Tools that fetch a model or engine on first use, such as the background remover, need one run first.) A tool that processes locally keeps working. A tool that uploads fails at once. This also catches the case where a site processes locally but "phones home" with the result.

What Stayput looks like in the panel

On any Stayput tool you will see the page and its scripts load, on the HEIC and JPEG XL pages one larger GET for the decoder program, and a few small anonymous usage-count requests to our own stats server. After you add files: nothing, apart from the same small counts when you add files and when a tool finishes, which name the tool and give rough ranges such as file count and size, never a file name or contents (the full list is on the privacy page). Each tool page also runs this count for you and lists the requests under "Open the network tab. Your files never appear in it." The site is open source, so the third check is reading the code.

What popular upload-based services say they do

The check tells you whether a file leaves; a service’s own policy tells you what happens to it after. We have summarised the published policies of the most searched-for converters, with deletion times, storage location and ads, from their own pages:

• CloudConvert, FreeConvert, Convertio and Zamzar for general file conversion.
• iLovePDF, Smallpdf and PDF24 for PDFs.
• Ezgif for GIFs and short video edits.
• remove.bg for background removal.

Questions