The melody of Baby by Justin Bieber runs 398 notes across 84 bars, 2:42 long in Ab at 132 beats per minute. The tab sits low on the neck, mostly under the fourth fret, one note at a time — no chords to barre and no strumming pattern to keep up with. A piano backing track plays the chords and bass underneath, so the line you are learning sounds like the record even at half speed.
Prefer to strum and sing it instead? Baby chords and lyrics.