Polar is a personal knowledge repository for PDF and web content supporting incremental reading and document annotation.
Clone or download
Type Name Latest commit message Commit time
Failed to load latest commit information.
.circleci ... Jan 16, 2019
.github/ISSUE_TEMPLATE Update issue templates Oct 31, 2018
apps better tags sorting to find new docs without tags to handle bulk impo… Jan 18, 2019
bootstrap4-glyphicons this migration to bootstrap v4 is silly.. Jun 16, 2018
build upgraded more strings.. Dec 3, 2018
docs - Update to electron 3.1.1 Jan 18, 2019
htmlviewer Fixed bug with PDF viewer where it couldn't initialize at the right z… Jan 12, 2019
pdfviewer-custom Fixed bug with PDF viewer where it couldn't initialize at the right z… Jan 12, 2019
pdfviewer Fixed bug with PDF viewer where it couldn't initialize at the right z… Jan 12, 2019
scripts ... revert channel fix.. Jan 8, 2019
web cleanup of Model Jan 18, 2019
.gitignore Merge branch 'burton-typescript' Aug 7, 2018
LICENSE.txt add GPL v3 txt to project so it's clear which version of the GPL we'r… Oct 17, 2018
README.md ... Jan 18, 2019
dev-app-update.yml version update metadata... Dec 19, 2018
electron-builder.yml setting font size for comment boxes, etc. Jan 5, 2019
icon.ico ... Jun 9, 2018
icon.png got super distracted today.. Jun 8, 2018
icon.svg got super distracted today.. Jun 8, 2018
main.ts should have a fix to the file URL problem Dec 11, 2018
package-lock.json - Update to electron 3.1.1 Jan 18, 2019
package.json - Update to electron 3.1.1 Jan 18, 2019
test.html inline style elements that may have been added dynamically by code...… Jan 16, 2019
tsconfig.json no longer list the emitted files... Jan 16, 2019
tslint.yaml moved toaster to ui/ Jan 6, 2019


Polar Bookshelf

Polar Bookshelf is personal knowledge repository which supports advanced features like incremental reading, annotation, comments, and spaced repetition. It supports reading PDF and the web content and was created using the Electron framework and PDF.js


  • PDF support We have first-class PDF support thanks to PDF.js. PDFs work well when reading content in book format or when reading scientific research which is often stored as PDF.

  • Captured Web Pages Download HTML content and save them as offline documents which can be annotated.

  • Pagemarks Easily keep track of what you're reading and the progress of each document.

  • Text Highlights Highlight text in PDF and web pages.

  • Area Highlights Capture a region of the page as a highlight which can be a chart, figure, infographic, etc.

  • Local Storage All content is stored locally. You can also use a system like git or Dropbox to transfer your repository across machines.

  • Hackable The entire system is based on Electron, Node, pdf.js, React and other web standards. If you're a developer - welcome home!

  • Standards Based All content is stored as JSON in a well documented schema. Annotations never mutate the original content.

  • Portable Run across any platform. Linux, MacOS, and Windows supported. We also product snaps which means you can install our .deb files on Ubuntu or Debian but also any Linux distribution that supports snaps!


PDF Document Polar has excellent PDF support.

Captured Web Content

Captured Web Content Polar supports fetching and storing web content locally for annotating.


Annotations Annotating a PDF including pagemarks showing content already read, an area highlight, and a text highlight.


Repository Polar includes a document repository manager to manage all your documents, open up a new editor, sort them as a queue or by priority, etc.


Packages for Windows, MacOS, and Linux are available on the downloads page.

We also have a CHANGELOG available if you're interested into what went into each release.


We have both a Discord group and Reddit group if you want to discuss Polar.

If it's a very technical issue it might be best to create a Github Issue.

Personal Knowledge Repository

Polar is a document manager for PDF and web content as well as a personal knowledge repository.

Polar allows you to keep all important reading material in one place including annotations and flashcards for spaced repetition.

It supports for features like pagemarks, text highlights, and progress tracking by keeping track of how much you've read including restoring pagemarks when you re-open documents.

Pagemarks are a new concept for tracking your reading inspired from incremental reading. They allow suspend and resume of reading for weeks and months in the future until you're ready to resume, without losing your place.

Since you can create multiple pagemarks they work even if you jump around in a book (which is often in technical or research work).

Web Content

PDF is an excellent document format but we've found that many HTML pages don't convert to PDF well since they were not intended to be printed.

Captured pages contain HTML content stored in phz (Polar HTML zip) files.

We fetch all resources, render the page as DOM and apply CSS, then de-activate the page by removing all scripts.

We then store the content in the phz archive format and serve the content directly to Electron.

This means you have long term storage for all your content. You can annotate it and use pagemarks without risk of the content changing.

To capture a new page just select File | Capture Web Page then enter a URL.

After that the page will be captured and then loaded.

Local Storage

All annotations, documents, PHZ files and other data are persisted on disk in your ~/.polar directory (different on each platform) and when you re-open a PDF or PHZ file your pagemarks and other annotations are restored.

Since storage is local you're not reliant on one specific cloud provider. You can also use tools like git or Dropbox to synchronize across machines.

Text Highlights

Text Highlight

Text highlights allow you to work with content like you're using a text highlighter in a book.

Create a text highlight.

Select text you want to highlight then hit Ctrl-Alt-T

Delete a text highlight.

Right click the highlight and select delete.

Key bindings:

  • Ctrl-Alt-T - create a new text highlight from the current selected text.

Area Highlights

Area Highlight

Area highlights allow you highlight a figure, infographic, or anything visual in a document.

Create an area highlight.

Right click on a page and select "Create area highlight"

Delete an highlight.

Right click the highlight and select delete.



Flashcards allow you to retain information long term by using a spaced repetition system like Anki to continually re-train yourself on material you want to retain.

Flashcards can be created by right clicking an annotation and selecting "Create Flashcard". The resulting flashcards are stored as annotations in your repository.


This is currently a beta feature and we're working on implementing Anki sync to enable spaced repetition. Any flashcards created now will be stored with Anki in the future.

Polar is very reliable to use for day to day PDF and web content annotation.

We're expecting to release a 1.0 in Sept 2018 with Anki sync support and initial annotation support.


Since the entire platform is based on Electron (Node + Chromium) the platform is very easy to work with which means developers can contribute easily.

Feel free to fork and send a pull request if there's some interesting feature you would like to add. Here is a list of good newcomer issues.


All data is stored on disk in JSON format. This also includes extracted metadata from the document. For example, text highlights include the source text that you copied as well as pointers into the original document where they can be found.


We believe the following design principles are core to seeing this as a successful project.

  • All the data should support long term file formats. The on disk format we use is JSON.

  • Portability to all platforms is critical. We're initially targeting Linux (Ubuntu), MacOS, and Windows. You shouldn't have to pick a tool, which you might be using for the next 5-10 years, and then get stuck to a platform which may or may not exist in the future.

Build from source

Install NodeJS and npm for your platform.

To run:

$ git clone https://github.com/burtonator/polar-bookshelf
$ cd polar-bookshelf
$ npm install && npm start


Polar is supported by community donations

All donations go to supporting Polar which include website hosting costs, web designer costs, continual integration services, etc.


This project exists thanks to all the people who contribute.


Thank you to all our backers! 🙏 [Become a backer]


Support this project by becoming a sponsor. Your logo will show up here with a link to your website. [Become a sponsor]


Polar is distributed under the GPL license.

PDF.js is available under Apache License. Electron is released under MIT License. Rest of the code is MIT licensed.

Icons made by Freepik from www.flaticon.com is licensed by CC 3.0 BY