The largest increase was in Cardiff, increasing from 11.1% in 2011 to 12.2% in 2021, which is an increase of around 6,000 people able to speak Welsh.
Roedd y cynnydd mwyaf yng Nghaerdydd, o 11.1% yn 2011 i 12.2% yn 2021, sef cynnydd o tua 6,000 o bobl sy'n gallu siarad Cymraeg.