You need to open a ZIP or RAR file, you don't want to install software for a one-time task, so you search "extract files online" — and then a nagging thought hits: is it actually safe to hand your files over to some website you've never heard of?
It's a fair question, and the honest answer is: it depends entirely on how the tool works.
The Two Very Different Kinds of "Online" Extractors
Most tools that call themselves "online extractors" work the same way: you upload your archive to their server, their server unpacks it, and then you download the extracted files back. This means your files — potentially containing tax documents, personal photos, work contracts, or anything else — physically travel to a computer you don't control and sit there, even briefly.
That's not inherently malicious, but it does introduce real risk:
- You don't know how long the file is stored, or where
- You're trusting an unknown company's security practices
- If the site is compromised, your files could be exposed
- Some free tools monetize by scanning or reselling data
The second kind of tool works completely differently: it processes your file inside your own browser, using a technology called WebAssembly (WASM). Nothing is uploaded anywhere. The extraction logic runs as code on your device, using your device's own processing power, exactly like a desktop app would — except it happens in a browser tab instead of an installed program.
This is how unpk.app works. It supports ZIP, RAR, 7Z, TAR.GZ, ISO, ZST, BZ2, and more, and every one of them is extracted locally. Nothing about your files is ever sent to a server.
Why Client-Side Processing Matters
The distinction isn't just marketing language — it changes what's actually possible for a bad actor:
- Server-based tools: your file exists, even temporarily, on infrastructure outside your control
- Client-side (WebAssembly) tools: your file never leaves your device — there's nothing to intercept, store, or leak, because there's no upload step to begin with
You can read more about exactly how this works on our Privacy page.
How to Verify a Tool Is Actually Local
You don't have to take any site's word for it. Here's a simple test that works on almost any client-side tool:
- Load the extractor page fully
- Turn off your Wi-Fi or disconnect from the internet
- Try dragging in your file
If the extraction still works with no internet connection, the processing is genuinely happening on your device — there's no server to talk to. If it fails or spins forever, it was relying on an upload the whole time.
Try this on unpk.app and you'll see it keeps working offline, because the WebAssembly engine is already loaded in your browser and never needs to phone home.
The Bottom Line
Online extraction isn't inherently unsafe — but "online" can mean two very different architectures. If your files contain anything sensitive (and honestly, most files do), stick to tools that process everything locally in the browser rather than uploading to a server.
Ready to try it yourself? Extract your file with unpk.app and check our Privacy page for the full technical explanation of how local extraction works.