Search “free PDF converter” and you'll find dozens of sites. Most are genuinely free to use, but they pay their bills the usual way: your file is uploaded to a server, the page is wrapped in ads, daily limits nudge you toward a subscription, and some stamp a watermark on free output.
FernPDF is free for a different reason, there's no server cost to cover, because nothing is uploaded. Every tool runs in your browser, with no ads, no watermarks, and no daily caps.
FernPDF
Free PDF websites
Where files are processed
On your device, in the browser, never uploaded
Uploaded to the site's servers for processing
Ads
None
Typically ad-supported, sometimes heavily
Watermarks on output
Never
Sometimes applied to free output
Daily limits
None, unlimited
Common, with upsells to remove them
Privacy
Structural, there's no upload to leak
Policy-based, you trust their retention promise
Works offline
Yes, after the page loads
No, needs the upload round-trip
Competitor details describe their publicly documented, server-based architecture in general terms and may change. Always check their current terms and pricing.
Where Free PDF websites can be stronger
Some free sites offer niche conversions that need a server engine
No client-side memory limits, since the heavy lifting runs on their servers
Occasionally a wider one-off tool selection
The honest verdict
A free upload-based site can be fine for a quick, non-sensitive file you don't mind sending to a server full of ads.
FernPDF is the better default for everything else: it's free with no ads, no watermark, and no limits, and your document never leaves your device.
FAQ
Because there's no server doing the work, your browser does it. No upload bandwidth, no processing servers, so no ad-revenue or subscription needed to cover them for the core tools.
Some do on their free tier and remove them on paid plans. FernPDF never watermarks output.
Reputable ones delete uploads after a while, but you're trusting a policy you can't observe. A tool that never uploads removes that risk entirely.