Archives and data files
Archives and spreadsheets are the containers that other files travel in. Someone sends a RAR file and your computer has no program to open it; a colleague exports a report as CSV and you need it as JSON for a script, or the other way round. The archive tool opens ZIP, RAR, 7Z and TAR files and lets you preview and download what's inside, and the data converter moves tables between CSV, XLSX and JSON with a preview before you save.
Both read the file in your browser. An archive full of personal documents, or a spreadsheet of customer records, stays on your device.
Device checks before a call or a purchase
The device tests answer quick questions: is my camera working and at what resolution, is the microphone picking up my voice, does every key on this keyboard register. They use the browser's own access to your hardware, which you grant with the usual permission prompt, and nothing is recorded or sent anywhere. They are useful before a video interview, when setting up a new laptop, or when checking a second-hand keyboard for dead keys.
Why no installation is needed
Each of these jobs used to need a desktop program. Browsers can now read archive formats with WebAssembly libraries, parse spreadsheets in JavaScript and talk to cameras and microphones through standard APIs, so a web page can do the same work. You can confirm that files are not uploaded by watching the Network tab in your browser's developer tools while a tool runs.
Good to know
Archives can contain files from people you do not know, so preview before you open anything executable, and remember that extracting in the browser never runs the files it contains. When converting spreadsheets, check the preview for dates and numbers stored as text, which are the most common cause of surprises after a conversion. Device tests need a browser permission each time, and you can revoke it from the address bar.