Do I need a username?
No, a username is optional. Telegram works completely without one. What it changes is how people reach you, and for most people that turns out to be worth having.
Without a username
People need your phone number to start a conversation, or you need to share a group or an invite. That is fine if you only talk to people you already know.
With a username
- Anyone can find you by searching @yourname.
- You get a public link, t.me/yourname, that works in a browser, an email signature or on a card.
- Your phone number stays private. Someone who messages you through your username never sees it.
Who should set one
If you want to be reachable by people who should not have your number, which covers anyone doing business, selling, running a community, freelancing or publishing anything, a username is the mechanism for that. If you only message family and colleagues who already have your number, you can skip it.
It also protects your name
Usernames are unique and first come, first served. Claiming the one that matches your name or brand keeps somebody else from taking it, which matters more than it sounds: an impersonator holding the obvious username is considerably more convincing than one holding an awkward variation of it.