This document is under construction and still evolving.

Polar Mission Statement and Design for a Personal Knowledge Repository

Polar has a broad mission statement to provide high quality tools for document annotation, management of documents (tagging, storage, etc) and sharing of content.

There’s a great deal of overlap in the technical requirements needed for these features so Polar provides a great deal of functionality to provide a comprehensive personal knowledge repository and distributed content management platform.


See the roadmap for Q2/Q3/Q4 2019.

The roadmap living document so please check back over time to see how it evolves especially as new features are released.

Use Cases

Polar focuses on a number of key use cases.

The core is document management which provides about 70% of the technical complexity and allows us to re-use this infrastructure for the other use cases.

Each additional use case builds upon but shares the core functionality to avoid technical complications.

Document Management

Document management is used by nearly all additional layers within Polar. This includes basic functionality like adding documents, supporting multiple formats, storing metadata (title, author, etc) and handles replication, document integrity, etc.

Functionally, this includes features like tagging, flagging, archiving, updating metadata, etc.

Incremental Reading

Allows the user to keep track of their position using pagemarks, update their pagemarks as they read documents, find new documents to read, etc.

We also keep track of core stats including number or documents read per day, etc to encourage the user to hit their reading goals.


Supports text and area highlighting, comments, flashcards, etc. The user can attach annotations directly to documents.

Annotations are top level metadata and can be exported, copied, and shared between users.

Document Sharing and Collaboration

Document sharing allows others to view and share documents you’re reading, and annotating.

This is a key Polar function as we want to test collaborative sharing to improve knowledge retention using flashcards, and annotations to allow users who are sharing the same documents to actively collaborate towards a better experience.

For example, users could collaboratively build flashcards, add video, etc.

We could also use this to automatically suggest flashcards for users of documents that are being shared with Polar.

This way you could add a text-book and have pre-built flashcards already compiled and easily added with one click.

Bibliography Management

This is primarily used for the scientific community and involves lookup of document metadata via DOI, preserving extended metadata including author information, and supports exporting selected documents as a bibliography.

Web Archival

Annotating web content is irrelevant if the document can be deleted by the site thereby invalidating your annotations.

Polar supports storing web content offline supporting annotations against content that may or may not be deleted (or updated) by the original site.

We plan on extending this use case to both improve archival in general but also support more transparent archives that seem like real web pages within your web browser.

We also intend on supporting annotations for content which isn’t necessarily cached. This functionality should allow Polar to be used by more users as it should be much easier to annotate content when it’s just a native web page.

Spaced Repetition and Flashcard Management

Having all your reading at your fingertips is pointless if it’s quickly forgotten.

Polar currently implements spaced repetition by supporting easy flashcard creation and attaching these to text/area highlights directly.

The Flashcards can then be sync’d directly to Anki.

We tend to continue supporting Anki for power users for the forseeable future but also want to support basic spaced repetition within Polar directly.

This will help people who aren’t Anki power users get started with SR without having to commit to Anki, add the plugin, create an account for sync there, install the app on their phone, etc.

5D Internet

Polar provides a five dimensional (5D) web platform. We assert that the current Internet is three-dimensional (3D) with traditional pages and links forming nodes, edges and building a graph representation of the web.

We’re adding the following dimensions:

Fourth Dimension: Time

Polar supports a content addressable storage scheme where documents are represented by their hash, not URL.

This allows us to store web pages in portable web archive formats (bundled as one document) which can be stored in perpetuity.

This allows users to lookup content in their personal repository and have multiple copies of the document based on time.

When connected this provides for an Internet-scale Internet Archive whereby users are individually archiving portions of the Internet. [^internet-scale-archiving]

Fifth Dimension: Annotation

Users can annotate documents in Polar including adding text and area highlights, comments, and flashcards.

This data is valuable to the individual but also to the web community at large.

TODO: Expand on this in the future.

Federated Data

The underlying Polar data model is not specific to any type of network or storage infrastructure.

Beyond standards:

Web standards are only one part of what we’re trying to address. Without millions of users using Polar as a integral part of our workflow we will not be successful.

To that end we have to have to focus on growth, UI/UX, support, mobile, and accessibility.

Corporate and Non-Profit Setup

There will effectively be two organizations setup to support Polar.

PolarOrg will support Polar as an Open Source project.

PolarCom will sell cloud storage, private team sharing, and additional premium features.

It’s our goal that the vast majority of users using Polar will use the platform for free.

We’re trying to target roughly 95% of users on Polar will not pay and will be on a freemium model.

In order for Polar to be competitive there must be an economic component to continue funding development.

Otherwise, we risk our ideas and technology being stolen by other companies who wouldn’t aggressively support the rights (and goals) of our user base.

User Rights

Polar wants to aggressively support the rights of our user base.

We’re not interested in doing anything evil. Without your trust we believe this will hurt our mission.

This includes but is not limited to:

Data Portability

You should be able to easily access your data in easy to work with file formats and export to 3rd party services at any time.

You Data is Your Data

Polar will never attempt to take exclusive ownership of your data and will only pursue reasonable rights to access your data for your use or the use of our data partners (cloud service infrastructure) when you give us access.

Polar will require non-exclusive rights to have access to your data when using cloud services including sync to mobile, web, etc.

We may also engage in data partnerships which will be disclosed and will only do so for the benefits of our user base.

Basically, we’re not interested in doing anything evil and will only use your data for your benefit.


We will make reasonable attempts at making encrypting your data when reasonable and at rest.

We’re also investigating private encrypted end-to-end datastores for private and sensitive data.


We have every intention to continue to support desktop-only and offline-only usage where your data is not sync’d to the cloud.

If cloud-only features are built (for example full-text search) we will not force uses to use cloud services.


Federation allows Polar to tie in different backend storage providers which could have different properties, security and privacy features.

Polar supports federation through the concept of Datastores which provides a high level interface for reading and writing data, subscribing to events, etc.

Currently Polar supports three datastores:


Provides a local storage for the desktop app and allows user to read and write data without any major privacy considerations inherent with cloud.


Stores data in Google Firebase to provide cloud functionality including web and mobile support.


Provides a hybrid between Disk+Firebase for the desktop cloud sync across devices.

Future Datastores

Polar provides for a Datastore interface which means we can easily implement new technologies for data storage in the future.

Filecoin is an example of an attractive Datastore which we might implement in the future.

Long-Term Archival

Due to the importance of Polar data we’re committed to verifying that documents stored in Polar are preserved long-term.

This include selecting reliable file formats and using web standards as much as possible.

[^internet-scale-archiving] At some point we might allow users to share documents but there are privacy concerns we have to address here as web documents served to users might have PII data embedded within them and we also have to comply with local laws as well as be respectful of user privacy. Initially this ] functionality won’t be enabled but it’s a sub-project we’d like to pursue in the future and might be possible for some fraction of the documents indexed when we can identify that they have zero PII.

Posted on: 11 Apr 2019

Read. Learn. Study remotely.

A powerful knowledge manager for web pages, textbooks, PDFs, to read and study remotely.

Supports tagging, annotation, highlighting, reading progress, and makes it effortless to remember what you've learned. By yourself or in groups.