Are there such things as Welsh language fonts? Are those necessary for Welsh? I know it has a different alphabet, but I don't know how much it matters
There are! Not many, but public facing bodies in Wales have started doing it.
So, for the most part, it is possible to just use any old font designed for English. Welsh has three main differences that pose a greater or lesser amount of difficulty for an English font, to whit:
We do not use the letters K, Q, V, X, or Z. (We didn't used to have J either but we nicked it and we're not giving it back.) Not a problem, those are just extraneous.
We have extra letters, all of which once upon a time had their own glyphs; but, the printing press meant these were lost. Instead, they're now what we call diglyphs - a letter seemingly represented by two letters. These are Ch, Dd, Ff, Ng, Ll, Ph, Rh, and Th. Not a serious problem, but word processors do count these as separate letters rather than diglyphs, so context-sensitive.
The to bach - in English, the circumflex. When Welsh needs to differentiate between long and short vowels, it uses a circumflex over the long ones: â, ê, î, ô, û, ŵ, and ŷ. This one is frequently a problem, particularly for ŵ and ŷ.
So, for the most part, you can get by with standard fonts, with the caveat that the circumflexes can be tricky. But:
In 2017, the Welsh Government commissioned a Welsh-specific set of typefaces, and the result was a trio of fonts called Cymru Wales Sans, Cymru Wales Serif, and Cymru Wales Transport. They are super cool and they turn the diglyphs into single letters, among other things. Transport for Wales use the latter in all official signage now:
And then as of 2023, Museum of Wales created a font called Amgueddfa Headline Cymru for its new logo that's Welsh only and uses the diglyphs properly:
I was in the Waterfront Museum today, and they've put up some official Nadolig Llawen signs for Christmas. Those are in the same font, and the Ll in llawen has been diglyphed up into a single stacked letter for it too.
So, we're starting to see these things being created, but so far it's just those. Any font makers out there who fancy branching out, you'll get a very happy Welsh-speaking audience...