I know that the vikings used runes but I’m not sure if the Celtic people used runes too? Just asking out of curiosity.
I answered nearly the same question just a while ago. No the Celts in Britain didn't have runes, they had the Ogham Script.
As said there, all Germanic peoples used runes and in the case of Scandinavia they were in use 500 years before the 250 years of the Viking Age and another 800 years after it, not counting revivals.