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Concentric Sky

Viewer for Khan Academy

Viewer for Khan Academy was developed by Concentric Sky in Eugene Oregon free of charge. Concentric Sky develops educational software solutions for companies and organizations like Cengage Learning, Encyclopedia Britannica, National Geographic, and Junyo. Education is in our roots, and we felt like building Viewer for Khan Academy (and open sourcing it) was an opportunity to give back to the world. Enjoy.

This repository contains the source code for the Viewer for Khan Academy Android app available from Google Play and the Amazon Appstore.

Please see the issues section to report any bugs or feature requests and to see the list of known issues.

Table of Contents


The Basics

The build requires Maven v3.0.3+ and the Android SDK to be installed in your development environment. In addition you'll need to set the ANDROID_HOME environment variable to the location of your SDK:

export ANDROID_HOME=/Users/austinlally/opt/android/sdk
API Credentials

Khan Academy API credentials are stored outside the repo for security reasons, so copy over the sample file:

cp oauth_credentials.json.sample res/raw/oauth_credentials.json

Without a valid API key, most of the app will still run fine. When trying to log in, though, you'll be presented with a blank page and the text "OAuth error. Invalid consumer." To use user login features, register at and enter the appropriate values into oauth_credentials.json.

With Maven installed and configured and oauth_credentials.json in place, build as follows:

  • Run mvn clean install from the repository root directory to build the APK.
  • Run mvn clean install android:deploy android:run to install and run the app also.

NOTE: If you already have the app installed through the Play or Amazon store, you'll need to remove it before installing a custom built version.


There is a small python script to download the Khan Academy topic tree and build a database. We ship the application with a pre-built database to avoid a long initial startup time.

You'll want pip and virtualenv.

Initial setup:

cd etc/scripts
virtualenv --distribute env
source env/bin/activate
pip install -r requirements.txt

Each time you want to build a db:

cd etc/scripts

To build the new db with the app, copy the output of this script to res/raw/db.


This project relies on the following other free software:


Please fork this repository and contribute back using pull requests.

Any contributions, large or small, are welcomed and appreciated and will be thoroughly reviewed and discussed.


####GPL Version 3

Viewer for Khan Academy Copyright (C) 2012 Concentric Sky, Inc.

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see

For the full license text, follow the link above or see the LICENSE file.

About Concentric Sky

For nearly a decade, Concentric Sky has been building technology solutions that impact people everywhere. We work in the mobile, enterprise and web application spaces. Our team, based in Eugene Oregon, loves to solve complex problems. Concentric Sky believes in contributing back to our community and one of the ways we do that is by open sourcing our code on GitHub. Contact Concentric Sky at


An open source Android app for Khan Academy.




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