empty vessels make the most sound; the meowing cat does not catch the mouse
Proverb meaning that those who talk a lot or boast often accomplish little. The literal image is of a cat that meows instead of silently hunting.
He always talks big, but in reality he hasn't accomplished anything. Truly, 'the meowing cat does not catch the mouse.'
A traditional Japanese proverb. The exact origin is uncertain, but it is a well-known saying comparing noisy, boastful people to a cat that meows instead of silently catching mice.