If you're using it only to make your website work, then you don't need a cookie banner. However, if it's doing double-duty and is also being used to track user

If you're using it only to make your website work, then you don't need a cookie banner. However, if it's doing double-duty and is also being used to track users (or to speak technically: if it can be considered PII by GDPR), then you need consent before using it for the tracking part. GDPR doesn't apply for cookies, btw, it applies for any personal data. Someone above used "information stored using fridge magnets" as an example.