Use when the version you are using of the OpenLayers JavaScript client toolkit is 3 or later
General Information
OpenLayers is a JavaScript library that provides developers with an API for browser-based mapping. Using the latest technologies, the API claims a high-performance and feature-rich experience. OpenLayers makes it easy to put a dynamic map in any web page. It can display map tiles, vector data and markers loaded from any source. OpenLayers has been developed to further the use of geographic information of all kinds. It is completely free, Open Source JavaScript, released under the 2-clause BSD License (also known as the FreeBSD).
The OpenLayers library supports a wide variety of tile and vector formats including XYZ, WFS, WMS, KML, GML, and GeoJSON. Bing Maps and OSM base maps are supported. Access to the Google Maps API's base maps is available through a third party utility. Utilities for projections and transformations are also provided.
With v3.x, OpenLayers was completely rewritten, and as such the paradigm known from OpenLayers 2 has completely changed. The examples page is useful for beginners, and the API documentation is helpful in finding functions that are not exemplified. Both examples and API are available on the openlayers.org and update with every version.
Examples
Use the examples to get a feel for how the API works, and leverage the jsFiddle integration to try out other things.
latest release
http://openlayers.org/en/latest/examples/
master
http://openlayers.org/en/master/examples/
API
The API details all functions of the application, but some may be flagged as 'experimental' and may be deprecated or altered in future releases.
latest release
http://openlayers.org/en/latest/apidoc/
master
http://openlayers.org/en/master/apidoc/
Source Code
For advanced developers, the entire source code is available on GitHub. Due to being open source, the latest version of the API
Source (latest release)
https://github.com/openlayers/openlayers/releases/latest
Source (main)
https://github.com/openlayers/openlayers/tree/main
Issues
Known issues and logged issues are kept on GitHub.
https://github.com/openlayers/openlayers/issues
For information on tagging guidelines for OpenLayers questions see the Meta Q&A at http://meta.gis.stackexchange.com/questions/4425/updating-openlayers-openlayers-2-and-openlayers-3-tags
