my preferred name on university id

i have 3 first names, however, i only go by one of them in my day to day life. obviously for legal stuff i need to state my full name but i was wondering if on my uni card i can just have my preferred name on it or if i must have my full name?

It will depend on the particular university's policies, but in general I'd expect you to be able to specify a "known-as" name for most purposes other than the most formal things. That would hopefully extend to your university ID card.

It's not uncommon for people to go by something that's not their full first name -- it might be things like they use "Bill" rather than "William", or they go by a middle name rather than their first name; and sometimes it's because their given names don't match their gender identity.

To be sure, though, you'd need to check with your university. You might be able to specify a known-as name (perhaps called something like a "preferred forename") during the registration process.