You can't judge a book by its cover

Meaning

Appearances can be deceiving.

Usage

Encourages looking deeper before judging.

Origin & History

Origins and dates here are approximate summaries. Many idioms have disputed or unknown origins, and not every date has been checked against a historical dictionary, so treat specific dates and stories as a starting point rather than a citation.

Book buying where covers hide content.

Used since the 19th century to warn against superficial judgments.