As @hobu recently said in a #GDAL
email (plus some additions)
https://spatialreference.org/ is #1 on
- speed (super fast loading)
- the most the up-to-date (every 3 months, like #PROJ)
- no ads
- no-fuss
- no tracking
- no cookies
- easy-to-consume
spatial reference definitions website in the world :)
It has not only #EPSG systems, but also #ESRI, #IAU 2015, #IGNF, #NKG and #OGC authorities.
As open source, you can even run it in your machine.
Enjoy it!

