Are online file converters safe? How in-browser tools keep your files private

Search for “compress PDF” or “convert video to MP4” and most of the results work the same way: you choose a file, it travels across the internet to the company’s server, the server does the work, and you download the result. Your file, which might be a bank statement, a legal document or a family video, now sits on a computer you know nothing about. Many services say they delete files after an hour or a day. You have to take their word for it.

Tools that run in your browser take a different approach, and it is the approach used for nearly everything on Dharmdutt.com. This post explains how it works, what it can honestly promise, and how to check for yourself.

How an in-browser tool works

When you pick a file in a web page, the browser lets that page read it, but only on your computer. A page can then process the file with code that runs locally:

Plain JavaScript handles jobs like resizing an image or merging PDF pages, using the same drawing and file features browsers use for everything else.
WebAssembly lets browsers run serious software at close to native speed. Our video tools use a build of the well-known ffmpeg program compiled to WebAssembly, so the same engine that powers desktop converters runs inside your browser tab.

The result is created in memory and offered as a download. At no point does the file have to leave your device, so there is no copy for anyone to keep, lose or leak.

What you gain

Privacy. Sensitive documents and photos never reach a third party.
No size queue. There is no upload to wait for, which matters for a multi-gigabyte video.
It keeps working on a slow connection once the page and its components have loaded.
No accounts or limits per day. Nobody is metering a server on your behalf.

What it cannot promise

Honest tools say where the limits are, so here are ours.

It uses your device’s memory and processor. A very large file can exceed what a browser tab is allowed to use, and some jobs, like re-encoding long HD video, are slower on one processor thread than on a desktop program or a server farm. The video pages warn you about this and let you convert just part of a video.
Some components load from the internet. The video engine, the PDF reading library and the HEIC converter are downloaded from public content delivery networks the first time you use them, so you need a connection to start. The file you are converting is not sent to those networks.
A few features do need a server. For example, the optional feedback form sends your message, and any attachment you add, to us. The privacy policy lists these exceptions.
Browsers differ. A format one browser can read or write, such as AVIF or WebP saving, may be missing in another, and the tools tell you when that happens.

How to check any tool for yourself

You do not have to trust a claim of “private”. You can watch what a page does:

Open the tool, then open your browser’s developer tools (press F12, or Ctrl+Shift+I) and choose the Network tab.
Pick your file and run the tool.
Look at the requests that appear. A true in-browser tool shows no request carrying your file. An upload-based service shows a large request, often to an address with “upload” in it, whose size matches your file.

Another quick test: load the page, turn off your Wi-Fi, and try again. Tools that run locally still process the file, apart from components that had not yet been downloaded.

A habit worth keeping. For anything confidential, such as an ID card scan, a contract or a medical report, prefer tools that work locally, and avoid sign-in-required online converters. If you must use an upload-based service, read how long it keeps files and whether it says who can access them.

Try it on a real file

If you have a large PDF to shrink, try Compress PDF and watch the Network tab. For a photo, use the image resizer. For a video that will not play on your phone, see our guide to converting to MP4 and the MKV to MP4 converter.