How do I get promoted when I'm good at my job but bad at selling myself?

Watching less capable people rise past you because they talk a better game is a special kind of frustrating. You did the honest thing, you got good at the actual work, and it feels like the world rewarded the wrong skill. That is a fair thing to be sore about. But the lesson underneath is useful. Selling yourself is not lying or bragging. It is making sure the right people can see work they would otherwise miss. You would not call it dishonest for a good product to have a clear label. Your work deserves a clear label too. Telling your boss plainly what you did and why it mattered is not showing off. It is just letting the truth be seen. Start small and factual. Keep a simple list of what you accomplish. In reviews and check-ins, say it plainly, no drama. Speak up in the meeting instead of after it. You do not have to become someone loud and fake. You just have to stop hiding good work and let it stand where it can be counted.