Uploading a scan of your ID, a signed contract, or a payslip to an online converter is something most people do without thinking — but it is genuinely a trust decision. How long does your file stay on that server? Who can access it? Are you sure it was deleted?
The cleanest way to answer those questions is to make them irrelevant: if the file is never uploaded, none of them apply.
Two different architectures
| Server-side processing | In-browser processing | |
|---|---|---|
| Where the file goes | Uploaded to a remote server | Never leaves your device |
| Internet required | Yes, throughout | Only to load the page |
| File size limit | Usually capped (upload limit) | Bounded by your device memory |
| Privacy risk | You must trust the provider | Structurally absent |
| Speed | Upload + download time | Instant, no transfer |
How to verify the claim yourself
A site's claim that "your files are not uploaded" is an auditable claim. Your browser's developer tools will tell you definitively:
- Press F12 on the page (or right-click → Inspect)
- Switch to the "Network" tab and clear the list
- Select your file and start the operation
- Look at the outgoing requests: is there a POST request roughly the size of your file?
An even stronger check: go offline
There is a more conclusive test. Load the page, then cut your internet connection entirely (Wi-Fi off / airplane mode). If the tool still works, your file is going nowhere — because there is nowhere for it to go. This gives you a clearer answer than any privacy policy ever could.
The limits of in-browser processing
To be honest, this approach has real limitations, and they are worth knowing:
- Very large files (hundreds of MB of video) can strain your device memory
- Processing power depends on your device — video compression is slow on an old phone
- Some heavy operations (OCR, advanced AI models) download a few MB of model files on first use
- If you close the tab, the operation stops — there is no server to continue it
Practical advice
For a non-sensitive, publicly shareable image, the tool you pick hardly matters. But for identity documents, contracts, medical reports or financial records, the architecture matters. Spending two minutes on the Network test above before processing such a file is far cheaper than regretting it later.
Every tool on this site runs inside your browser and passes both tests above. Feel free to check right now.