diff --git a/README.md b/README.md
index ed259d9..8aa3568 100644
--- a/README.md
+++ b/README.md
@@ -3,4 +3,9 @@
 PMTiles is a single-file archive format for tiled data. A PMTiles archive can be hosted on a commodity storage platform such as S3, and enables low-cost, zero-maintenance map applications that are "serverless" - free of a custom tile backend or third party provider.
 
 See also:
-* [Cloud Optimized GeoTIFFs](https://www.cogeo.org) 
\ No newline at end of file
+* [Cloud Optimized GeoTIFFs](https://www.cogeo.org)
+
+
+## License
+
+The reference implementations of PMTiles are published under the BSD 3-Clause License. The PMTiles specification itself is public domain, or under a CC0 license where applicable.