From the WikiTech-L Listserv:
Using this service you can browse and embed map tiles into your own tools using OpenStreetMap data.
Currently, we handle traffic from *.wmflabs .org and *.wikivoyage .org (referrer header must be either missing or set to these values) but we would like to open it up to Wikipedia traffic if we see enough use.
Our hope is that this service fits the needs of the numerous maps developers and tool authors who have asked for a WMF hosted tile service with an initial focus on WikiVoyage.
We’d love for you to try our new service, experiment writing tools using our tiles, and giving us feedback.
If you’ve built a tool using OpenStreetMap-based imagery then using our service is a simple drop-in replacement. Getting started is as easy as https://www.mediawiki.org/wiki/Maps#Getting_Started
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See Also: Learn More About This Project