you can't tell a book by its cover

you can't tell a book by its cover

proverb You can't base your opinion of something (or someone) on the way it (or one) looks. A variant of "don't judge a book by its cover." This report may look dull, but you can't tell a book by its cover—I will have you riveted by the facts and figures in no time! I know she's a little frumpy, but you can't tell a book by its cover, man!
See also: book, by, cover, tell
Farlex Dictionary of Idioms.
See also:
  • teach a man to fish
  • it takes a village
  • village
  • the best-laid plans
  • the best-laid plans go astray
  • the best-laid plans of mice and men
  • best-laid plans go astray, the
  • a little knowledge is a dangerous thing
  • a little learning is a dangerous thing
  • better bend than break