The Welsh-language edition, entitled Gwyddoniadur Cymru is regarded as the most ambitious encyclopaedic work to be published in Welsh since the 19th century.
In this respect it is more like the Cymru: Yn Hanesyddol, Parthedegol, A Bywgraphyddol ("Wales: Historical, Regional, & Biographical"), edited by Owen Jones and published between 1871 and 1875.
With everything you could think of about Wales in [the encyclopaedia]," adding "Every town, every village, every city is mentioned in there," and including famous people in the fields of science, religion, politics, popular culture, amongst others.
The encyclopaedia's content includes a number of Welsh "firsts", as well as key facts, such as: the equals sign was created by Welshman Robert Recorde of Tenby in the 1540s; Felinfoel was the first brewery to can beer in Europe; the nearest point between Wales and Ireland is the lighthouse on Strumble Head; Wales' largest metal dragon is in Newport; Newtown had the first mail order service in Great Britain; The world's tallest mountain was named after Welshman Sir George Everest; Swansea is the wettest city in Great Britain; the world's rarest apple was discovered on Bardsey Island in 2000; Wales produces more energy than it consumes.
Some reviewers have suggested that the choice of subjects, and how some articles related to politics are worded, is not completely balanced, and that there should be more coverage of the role of the British labour movement.