The responsibility for advising on the standard forms of Welsh place-names lies with the Welsh Language Commissioner.
Whilst the Welsh Language Commissioner’s new website was being developed, the Welsh Government hosted the List of Standardised Welsh Place-names on this page on the BydTermCymru site.
The Welsh Language Commissioner's new website is now live, and the List is now being maintained on that website. The list will not be published on BydTermCymru anymore.
Go to the Commissioner's website to get the latest version of the List, and make that page one of your favourites.