Edit text in place, sign, redact, reorganize. True content-stream rewrite, not stamp-on-top.
LaunchEdit, sign, redact, and reorganize PDF files in your browser. The Adobe Acrobat alternative that runs on your device — no upload, no subscription.
Pixel-perfect PDF diff with word-level text view, metadata + form-field compare, ruler, and exclusion zones.
LaunchSide-by-side or overlay PDF diff with a document-type selector — Document (contracts, reports), AEC / Blueprint (drawings, schematics), or Image-Scan. Highlights pixel-level differences plus a word-level text diff in a modal.
Open any PCB Gerber bundle in your browser. Gerber X2, Excellon, layer compare, snap-to-pad measure, snapshot URLs.
LaunchOpen RS-274X / X2 Gerber and Excellon files. Inspect layers, measure traces, export to PNG / SVG / DXF.
Compress, merge, split, convert, and manipulate PDF files.
Resize, compress, convert, and transform images.
Format, encode, decode, and validate code and data — safe for production secrets.
Convert, compress, and cut audio and video — MP3, WAV, MP4, WebM, Opus — all in your browser, nothing uploads.
Sourdough baker math, canning processing times — kitchen math you should not memorize.
AES-256 file encryption and self-destructing encrypted notes.
Analyze packet captures and run sysadmin diagnostics in your browser — nothing uploads. PCAP Analyzer ships first.
Chart-overlay technical analysis and precision financial math — your screenshots and numbers never leave your device.
Open CAD, BIM, medical, and enterprise files without paying $300-30K/year for the native software. Gerber Viewer ships first.
Most "free online" PDF tools quietly upload your file to their server. Here is the 30-second check you can run in any browser, with screenshots, that proves whether a given tool ever sends your file off your device.
A PDF tool is “uploading your file” when the browser sends the bytes of that file to a server you don’t control. You can see this happen, or fail to happen, by opening your browser’s DevTools and watching the Network tab while the tool runs.
Thirty seconds. Every modern browser. Works on us, works on every competitor we checked.
What you’ll need
- Any desktop browser (Chrome, Edge, Firefox, Safari, Arc).
- A PDF file you don’t mind feeding to the tool — pick something recognisable, 5–10 MB is ideal.
- Roughly thirty seconds.
Press F12 on Windows or Linux, or Cmd + Option + I on Mac. A panel opens at the bottom or side of the browser. The exact layout differs slightly per browser, but every modern one has a tab labelled Network. Click it. You may see the message “Recording network activity… Perform a request or hit Ctrl+E to start recording” — that’s normal. Refresh the page once with DevTools open so the recording starts clean.
The Network tab is the browser’s own log of every request the page makes. It’s not editable by the page. The site can’t lie to it. Whatever shows up there really happened, in the order it shows.
Drop your PDF onto the tool. Let it finish. Look at the Network panel.
A privacy-clean tool — one that processes the file locally — shows you two kinds of rows in that list:
POST to a small first-party analytics endpoint on the
same domain, carrying the tool slug, a duration in milliseconds, and
your file size rounded to coarse size buckets, rounded hard — never
the real byte count. The Size column reads well under 1 KB — a few
dozen to a couple hundred bytes. That’s it.What you should not see, on a privacy-clean tool, is a request the size of your file. If you fed it a 7 MB PDF and there’s a 7 MB row in the list, that’s the upload. The browser is showing you the receipt.
Click the Method filter and select POST, or type method:POST
into the filter box. POST is the HTTP verb browsers use to send data up
to a server. GET fetches code and assets down. Filtering on POST cuts
out the noise of code loading and shows you only the requests that could
plausibly carry your file.
A privacy-clean tool will show either zero POST rows, or a tiny one or
two for analytics, each well under 1 KB. A tool that’s uploading your
file shows a POST that’s the size of the file — usually labelled
multipart/form-data in the Type column, sent a few hundred
milliseconds after you dropped the file in. There’s no way to disguise
this. Browsers will tell you.
method:POST, the noise of code-loading falls away. Loft leaves two beacon rows of a few hundred bytes. The amber row is what a cloud tool would add — a multipart upload the size of your file, a few hundred milliseconds after you dropped it in — and it is simply absent here.For reference: when a tool genuinely uploads your file, the request shows
up with the file’s content type, a Size column matching the file size
(or slightly larger from form encoding), and usually a destination URL
that includes a word like upload, convert, process, or the
tool’s own subdomain. Click it. The Payload tab will literally show
you binary chunks of the file. The browser doesn’t hide this; it makes
it inspectable on purpose so users can verify what their pages are
doing.
There’s nothing inherently wrong with uploading — the tool has to do its job somehow. The point isn’t that upload is evil. The point is that you, the user, deserve to know which one you’re using before you drop a tax return or a signed contract into it.
DevTools → Application tab → Service Workers in the left sidebar. A service worker is a small script the browser keeps running in the background so a page can still respond when you’re offline. If a tool truly does its work locally, it has a strong incentive to register one. If it can’t work without a server, it doesn’t bother.
Loft registers a service worker (sw.js) on every page. You’ll see it
listed as activated and is running. Try disconnecting from Wi-Fi, then
reloading a pinned Loft tool — it’ll still open, still run.
sw.js shows activated and is running, with its offline cache namespaces listed below. A registered worker is the tell that a tool can keep working with the network off — cut your Wi-Fi and a pinned Loft tool still opens and runs.Application tab → IndexedDB in the left sidebar. IndexedDB is the browser’s local database — it’s where a page can store data on your machine that persists across visits. Loft uses it for pinned-tool metadata, OCR model files you opted to download, and any explicit “saved” outputs you asked the tool to keep. It does not store the content of files you ran through the tool, unless you specifically clicked save.
Click through the entries. You should see only the tool metadata you’d expect from how you’ve used the site. No mystery copies of files you processed.
A couple of nuances worth admitting:
If you spot something on the Loft Network tab that doesn’t match this post, send us a note. We’d rather fix wording than ship a misleading guide.
Five checks, every privacy-clean local tool passes them, every cloud wrapper fails at least one:
Content-Security-Policy. The form-action and connect-src
directives list every place the page is allowed to send data.No. The Network tab is part of the browser itself, not a feature of the website. A website cannot turn it off, edit its contents, or make requests invisible to it. If you see a POST listed, it happened. If you don’t, it didn’t.
DevTools logs WebSocket frames under a separate tab, beacon requests under Network, and Service Worker fetches under both Network and the Service Worker panel. There’s no documented way for a page to perform a network request that’s invisible to DevTools. Browser security researchers and bug-bounty programs would have a field day with one if it existed.
It’s the analytics beacon Loft uses to count how many people ran which
tool, how long it took, and roughly what file size bucket they were in.
The payload is well under 1 KB and carries no file content. The site
honours the Sec-GPC Global Privacy Control header — if your browser
sends it, the endpoint drops the write before storing anything.
Mostly inertia. Cloud-side processing was the standard pattern when these tools were built years ago, before browsers got fast WebAssembly and Web Workers. The infrastructure cost of processing files server-side also gives the operator a reason to ask for an email or show ads to recoup it. Local-first sidesteps both of those incentives, but it’s a deeper rewrite than most operators have wanted to do.
This is one of a series of explainer posts on how Loft Tools works. The pillar page collects the same checks alongside the architecture decisions that make them possible — start there if you want the whole picture in one scroll.