you can't judge a book by its cover
Proposed by a contributor, not yet supported by evidence.
Also seen as: you can't tell a book by its cover
Meaning · English
Recognized English idiom; full definition pending editorial review.
Where it’s used:
Used
Widespread English
Sources & notes
Listed in Wiktionary’s “English idioms” category (retrieved 2026-07-29); definition pending editorial review.
Common questions
What does “you can't judge a book by its cover” mean?
Recognized English idiom; full definition pending editorial review.
Is “you can't judge a book by its cover” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.