The main idea is the same as with a paper-bound book: you can leap to another page or document for a quick look-up while keeping your place on what you are reading. That split focus makes technical documents much easier to work through.

Web app (and Android wrapper via Capacitor) for viewing PDFs in a split layout: each pane can show any page of its own document, so you can compare two different PDFs side by side, or two pages from the same file.

The header is a slim strip: ☰ opens a flyout with Recent, Libraries, Export highlights & notes, Help, About, Panes (split vs single), and on narrow two-pane layouts View (stacked split vs tabs). Each PDF pane uses a floating ‹ page › bar and a ⋯ button (bottom-right) for open file, zoom, libraries, copy, highlight, notes, and marks. A floating Left / Right pill appears when only one pane is visible.

In the ☰ menu, Panes → Split shows Left and Right together. Panes → Single shows one pane at full width; use the floating Left / Right pill to switch slots. Stored in localStorage as leapReaderPaneMode (split or single; default split).

When the viewport is 720px wide or less and Panes → Split is selected, open ☰ and use View (stacked split vs tabs):

• Split — both panes stay visible (stacked vertically), same as before on a phone in portrait.
• Tabs — only one pane at a time; use Left / Right to switch. Handy when the window is too narrow for two previews.

Your choice is stored in the browser (localStorage key leapReaderLayout). On wide viewports with two panes, both columns show and View is hidden in the menu. In single-pane mode View is hidden (you always use one pane at a time).

• Recent — Every PDF you open is saved in IndexedDB (database name pdf-split-reader) so you can reopen it from Recent without picking the file again. Each row has Left and Right to choose which pane opens that file. Data stays on this browser / device only. Delete removes that copy from storage (and unlinks it from libraries); if that file was open in one or both panes, those panes are cleared.
• Libraries — Named collections of references to saved documents. Creating or deleting a library does not delete the underlying PDF from Recent unless you delete the document itself. Whenever you open a PDF (from disk, Recent, or Libraries), it is also added to an Imported library, which is created automatically the first time you need it. You can remove documents from Imported like any other library; opening the file again will add it back.
• Adding / removing PDFs in libraries — Add to library… / Remove from library… apply to the pane you last interacted with (tap or open a file in that pane first). The document must be in Recent. Same pair on each Recent row. In Libraries, each document row has Left / Right to open into a pane; each library has Add documents… and Remove documents… as before. Nothing here deletes the PDF from Recent unless you use Delete there.

Rough cap: about 80 distinct stored PDFs; oldest by last-opened time may be removed when you add new ones. Layout preferences use localStorage (leapReaderPaneMode, leapReaderLayout), separate from IndexedDB.

• Copy — Select text on a page (invisible PDF text layer over the canvas), then use the floating bar or ⋯ → Copy, or the browser’s normal copy shortcut. A short “Copied” toast appears when using the button.
• Highlight — With text selected, use the floating bar → Highlight (or ⋯). Pick a color, or Shift+click Highlight / Ctrl+Shift+H (⌘+Shift+H on Mac) to use the last color. Highlights are tied to page, left/right pane, and that pane’s document (saved library id, or unsaved:name:size for files not in Recent).
• Place note — Toggle Place note and tap a spot on the page, or select text and use Note on the floating bar / Ctrl+Shift+N (⌘+Shift+N on Mac) to drop a pin at the selection. A pin appears; tap it to read the note.
• Marks — Lists highlights and notes for all saved documents (not only the open panes), sorted by file name and page. Go opens the PDF in the pane where the mark was created and jumps to that page. Edit (notes only) does the same, then opens the note editor. Delete removes one mark.

Marks are not embedded in the PDF file. They are stored with the rest of app data: IndexedDB in the browser (annotations store, database pdf-split-reader v2), or annotations.json under the desktop app’s leap-reader-data folder. Deleting a document from Recent removes its marks as well.

Backup / export — In the ☰ menu, Export highlights & notes… downloads a JSON file (leap-reader-highlights-notes-*.json) listing every highlight and note grouped by stored document id and filename. Use it for archives, moving data to another machine, or custom tooling. There is no import yet; re-import would be a separate feature.

• Node.js 18+ and npm (for development and builds)
• Android: Android Studio, Android SDK, and a JDK compatible with Capacitor 7 (see Capacitor Android docs)

Wraps the built UI in a desktop window (Node + Electron). From the project root:

npm install
npm run desktop:build

Or, if dist/ is already built:

npm run desktop:start

On desktop, libraries, notes, highlights, and cached PDFs live in a real folder: leap-reader-data inside Electron’s userData directory (e.g. ~/.config/leap-reader/ on Linux). You will see libraries.json, annotations.json, manifest.json, and documents/*.pdf there. The first time you run this version, any data still in IndexedDB is copied into that folder once; the in-browser build continues to use IndexedDB only. If you upgraded from an older package name, copy flip-reader-data from the previous app config directory into leap-reader-data here to keep your files.

Wrapper scripts (install deps if needed, build if dist/ is missing, then start Electron):

chmod +x scripts/run-desktop.sh start-desktop   # once, on Unix
./scripts/run-desktop.sh
# or
./start-desktop

On Windows:

scripts\start-desktop.cmd

Or, if you have Bash (Git Bash, WSL):

npm run start:desktop

npm install
npm run desktop

This starts the Vite dev server and opens your default browser. Stop with Ctrl+C.

Without opening a browser:

npm run dev

Vite prints a local URL (and may listen on your LAN). Use the local URL for normal desktop use.

npm run build
npm run preview

Then open the URL Vite prints (use --open only if you add it to a custom script; the default preview script does not open a browser).

npm run build
npx cap sync android
npx cap open android

In Android Studio, run on a device or emulator. After changing web assets, run npm run build and npx cap sync android again.

The same information is in the app under ☰ → About.

• Contact: [email protected]
• Copyright: © 2026 Biplab Sarkar. All rights reserved.