Specifying the link to the official website for a feature.
The website=* tag can be used to provide the full URL to the official website for the related features, be it a building, park railway or anything else. A link to an relevant but unofficial alternative or additional resource can be created using url=*. A link to Wikipedia should use wikipedia=* (do however note the different format for wikipedia links which are not full URLs).
For small format websites (designed for smaller displays, reduced bandwidth, or mobile touchscreens) use website:mobile=*.
Avoid long URLs
Use as short an URL as possible. Choose simple URLs over complex URLs if they basically point to the same content. For example, use http://bahn.de/ instead of http://www.bahn.de/p/view/index.shtml, as both will get you to the front page. Websites are frequently redesigned, so strive for the most "robust" URL that works.
- RFC 1738 section 2 generic URL syntax
- RFC 1738 section 3.1 common Internet scheme syntax - the definition of the http and https URL schemes base on this
- RFC 1738 section 3.3 The http URL scheme
- RFC 2818 section 2.4 The https URL scheme
- Proposed features/External links - different tagging ideas for the same or similar
- url=* - A more general tag. Any URL which may be the official website or may be something else (e.g. wikipedia article)
- Key:contact - The contact:* namespace with contact:website=*
- OpenLinkMap  a slippy map, making this tag's data available as clickable POIs
- Keepright  where as of the year 2011 a project is underway to validate the content of website tags, ensuring they still match the osm object.
This tag is an external reference and is compatible with the tag2link plugin