A PDF toolbox that installs like a native app — desktop icon, dedicated window, files received straight from the operating system — without an app store or an account: that is what the PWA (Progressive Web App) format allows. Document Flare uses every part of it, including the rarest one: a fully working offline mode, after one online visit.
An app with no app store
A PWA is a website plus two pieces: a manifest (manifest.webmanifest), declaring the name, icons and standalone display — the app opens in its own window, no address bar — and a service worker, a script that sits between the app and the network. That worker makes everything else possible: install, file opening, offline.
The practical consequence: no store, no account, no third-party platform terms. Updates come from the site itself — and, as we will see, they are proposed, never forced.
Install in two clicks
- Open documentflare.com in Chrome or Edge, on desktop or Android.
- Click the install icon in the address bar — or, in the browser menu, “Install Document Flare” / “Add to Home screen”. On iOS, go through Safari: Share → “Add to Home Screen”.
- The app opens in its own window and joins the launcher, desktop or home screen, like any installed app.
An honest caveat: installation works everywhere, but the system integrations described next — direct file opening and share — belong to Chromium browsers. Safari installs the app without those handlers.
Open a PDF by double-clicking it
The manifest declares a file_handlers entry: action /?launch=open, for the application/pdf type and the .pdf extension. Once the app is installed under Chrome or Edge (version 102 or later, on desktop), right-clicking a PDF offers “Open with Document Flare” — and a double-click can make it the default handler.
The mechanics are entirely local: the browser exposes window.launchQueue; our LaunchQueueBridge reads the file handles, extracts the File objects and injects them into the workspace through an internal handoff store. The document is open, ready to be processed — it has transited through no server.
The manifest also declares a protocol handler for web+documentflare:: a compatible browser can associate those links with the app. A link like web+documentflare:merge-pdf opens the tool’s page directly — the slug is restricted to the catalogue’s identifier format, never an arbitrary path.
Receive a PDF from Android share
The manifest’s second handler, share_target: a multipart POST target at /share-target accepting application/pdf. In practice: from Android mail, scanner or file manager, “Share → Document Flare” drops the document into the app.
The path is defensive by construction. The service worker intercepts the POST — only if it is a navigation —, checks each file’s %PDF- signature, caps the share at 10 files and 100 MiB total, then places the files in a single-read buffer cache before redirecting to the workspace. The bridge reloads the files and the buffer is consumed: nothing persists after opening. Right after scanning, it is the ideal link — see our guide to scanning to PDF from mobile.
Offline after one online visit
The exact wording matters: Document Flare works offline after one online visit. On first load, the service worker precaches the whole application — 380 files, about 8.4 MiB: pre-rendered pages, code, icons, manifest. The precache proceeds file by file; a cut or a full quota leaves a “partial” state, recorded then automatically completed when the network returns.
After that, three strategies apply:
- Navigations: network first, falling back to the cached page, then to the app shell — never a blank page.
- App assets: served from cache, under a strict whitelist — no document byte can enter it.
- Heavy models: Tesseract OCR (worker, WASM core, French language — the four other languages on demand) and semantic search (~115 MiB of ONNX weights) download once while online, then persist in a dedicated cache that survives updates. If you open those tools offline without the model, the app says so before any processing — no silent failure.
Two discreet signals complete the setup: a badge appears only when offline or on a partial precache, and when a new version is ready a banner offers “Reload” or “Later” — the new service worker waits for your gesture, it never takes over mid-session.
The air-gapped scenario, for real
The consequence: after an online session that fetched the app and the models you want, you can cut the network — airplane mode, isolated workstation, air-gapped environment. The catalog’s 52 local tools work, and so does the history. And this is verifiable rather than claimed: in developer tools, Network tab, tick “Offline”, then process a PDF — everything runs, and no request carries the document. The Application → Cache Storage tab shows both caches, df-app-* and df-models-v1. The full anatomy of what a PDF upload really sends is in our article where do your files really go.
One acknowledged exception: seven tools marked as an “ephemeral remote service” — Word/Excel/PowerPoint/HTML to PDF conversions and back, AI summary — send the document to an ephemeral service after explicit consent. They require a connection, by construction, and refuse to run without one.
Local history: in IndexedDB, wiped in one gesture
The workspace history lives in IndexedDB, on your device: metadata plus result bytes, capped at 20 entries and ~25 MiB of retained bytes — beyond that, the oldest entries lose their bytes while metadata stays. The “Clear space” button purges that history entirely — file names and bytes — along with loaded files and favorites. Only the preferences that disable history survive: they are privacy settings, not data.
Honest limits
- One online visit is mandatory: nothing works offline from a cold start, and the precache is ~8.4 MiB of download.
- iOS: installation works via Safari, but direct file opening, the share target and the protocol handler are not supported.
- Remote tools: the seven conversions/summary tools stay out of reach without a connection.
- Browser AI: local translation and summary rely on Chrome/Edge 138+ built-in models, managed by the browser — not by our cache.
- Partial precache: after an interruption, the app stays usable online and completes its cache when the network returns — but offline is only guaranteed once the state is complete.
Going further
The pillar on PDF tools without upload details the local architecture; the article on local processing privacy formalizes the promise. To chain tools without re-uploading, see shareable recipes and batch processing. And if the stakes are professional secrecy, our verticals for lawyers, healthcare and HR apply these guarantees per trade.
