GeoFire is set of open-source libraries for JavaScript, Objective-C, and Java that allow you to store and query a set of keys based on their geographic location. At its heart, GeoFire simply stores locations with string keys. Its main benefit, however, is the possibility of retrieving only those keys within a given geographic area - all in realtime.

GeoFire uses the Firebase database for data storage, allowing query results to be updated in realtime as they change. GeoFire selectively loads only the data near certain locations, keeping your applications light and responsive, even with extremely large datasets.

The GeoFire library is available in three different languages:

• GeoFire for JavaScript
• GeoFire for Objective-C
• GeoFire for Java

All of the clients work on the same underlying data structure and have similar APIs, making it easy to create a cross-platform app on top of GeoFire.

GeoFire is designed as a lightweight add-on to Firebase. To keep things simple, GeoFire stores data in its own format and its own location within your Firebase database. This allows your existing data format and security rules to remain unchanged while still providing you with an easy solution for geo queries.

Assume you are building an app to rate bars and you store all information for a bar, e.g. name, business hours and price range, at /bars/<bar-id>. Later, you want to add the possibility for users to search for bars in their vicinity. This is where GeoFire comes in. You can store the location for each bar using GeoFire, using the bar IDs as GeoFire keys. GeoFire then allows you to easily query which bar IDs (the keys) are nearby. To display any additional information about the bars, you can load the information for each bar returned by the query at /bars/<bar-id>.

To see GeoFire in action, you can play around with our fully-featured JavaScript demo. (Drag the purple circle!) This demo maps all of the San Francisco MUNI vehicles within a certain search radius. You can drag around the search radius and see the vehicles update in realtime.

We wrote the same demo for the Objective-C and Java clients as well. The code for the demos is available in each client's respective repository.

GeoFire requires the Firebase database in order to store location data. You can sign up here for a free account.