VSCode PDF Viewer

Open .pdf files directly inside VS Code.

This extension uses Mozilla pdf.js and integrates it into a VS Code custom editor so PDF files can be previewed without leaving the editor.

Features

• Open PDF files in a built-in preview
• Auto-reload when the file changes on disk
• Document outline, thumbnails, and find-in-document
• Configurable default zoom, sidebar, cursor, scroll mode, and spread mode
• Works in untrusted workspaces

Settings

Available settings:

• pdf-preview.default.cursor
  • select or hand
• pdf-preview.default.scale
  • auto, page-actual, page-fit, page-width, or a numeric scale such as 1.25
• pdf-preview.default.sidebar
  • show or hide the sidebar on load
• pdf-preview.default.scrollMode
  • vertical, horizontal, or wrapped
• pdf-preview.default.spreadMode
  • none, odd, or even

Notes

• This extension is focused on in-editor PDF viewing.
• Rendering and viewer behavior are provided by the bundled pdf.js distribution.
• Current bundled pdf.js version: 5.6.205

Known limitations

• Large or complex PDFs may still be heavy, depending on the document and your machine.
• This extension does not aim to replace a full desktop PDF editor.

Maintainer notes

This extension does not build pdf.js from source. It vendors the upstream legacy distribution under lib/ and adapts it for a VS Code webview.

The main integration points are:

• src/pdfPreview.ts
  • creates the webview
  • reads upstream lib/web/viewer.html
  • injects the VS Code CSP, <base> tag, runtime config, and lib/main.js
• lib/main.js
  • bridges the upstream viewer to the extension
  • applies the extension defaults for cursor, zoom, sidebar, scroll mode, and spread mode
  • configures asset URLs for cmaps, standard_fonts, iccs, and wasm
  • handles file reload while preserving viewer state as much as possible
• lib/build/* and lib/web/*
  • vendored upstream assets from the pdf.js legacy dist

Notes on the 5.x migration

The jump from pdf.js 3.x to 5.6.205 is not a drop-in asset replacement.

The main changes are:

• the legacy dist is now ESM-based
  • pdf.js -> pdf.mjs
  • pdf.worker.js -> pdf.worker.mjs
  • viewer.js -> viewer.mjs
• viewer localization changed
  • locale.properties -> locale.json
  • per-locale files are now viewer.ftl
• additional runtime asset directories are required
  • web/iccs
  • web/wasm
• the upstream viewer UI and DOM structure changed significantly

Because of that, this extension no longer keeps a copied HTML template in TypeScript. It injects into the vendored upstream viewer.html at runtime.

Upgrading pdf.js

1. Download the new legacy distribution zip from a pdf.js release.
2. Extract it.
3. Replace the vendored upstream assets:
   • overwrite lib/build/*
   • overwrite lib/web/*
4. Remove the upstream sample PDF:
   • delete lib/web/compressed.tracemonkey-pldi-09.pdf
5. Disable the upstream sample default in lib/web/viewer.mjs:
   • set defaultOptions.defaultUrl.value to ""
6. Review the VS Code adaptation points:
   • src/pdfPreview.ts
   • lib/main.js
7. Rebuild and package:
   • npm run compile
   • npm run package

What to verify after an upgrade

• the viewer loads with styling applied
• the document opens without using the upstream sample PDF
• the worker loads correctly
• text selection works
• find works
• reloading the file from disk refreshes the preview without a broken state
• fonts, CMaps, ICC profiles, and wasm-backed features resolve without missing-asset errors

Credits

• Built on top of Mozilla pdf.js
• Originally based on tomoki1207/vscode-pdfviewer
• The pdf.js 5.6.205 migration and version-bump work in this fork was carried out with assistance from Codex

License

See LICENSE.