SHA-1 vs SHA-256: What's the Difference?

SHA-1 and SHA-256 are both hash functions from the SHA family, but one is broken and one is current. Use SHA-256.

The quick comparison

	SHA-1	SHA-256
Digest size	160 bits (40 hex chars)	256 bits (64 hex chars)
Year published	1995	2001
Family	SHA-1	SHA-2
Collision-resistant?	No (broken in 2017)	Yes
Recommended?	No	Yes

What the output looks like

The same input produces very different digests:

echo -n "hello" | sha1sum
# aaf4c61ddcc5e8a2dabede0f3b482cd9aea9434d

echo -n "hello" | sha256sum
# 2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824

SHA-256's longer digest is part of why it's harder to attack.

Why SHA-1 is deprecated

In 2017, researchers produced two different files with the same SHA-1 hash (the "SHACK" / SHAttered collision). A collision means an attacker can substitute a malicious file for a trusted one without changing the hash. That breaks SHA-1 for signatures, certificates, and integrity checks. Git still uses SHA-1 for object IDs but has added collision detection and is migrating to SHA-256.

When can you still see SHA-1?

For non-security uses — like a quick cache key or a checksum against accidental corruption — SHA-1 is fine and fast. The moment security matters (signatures, deduplication an attacker could exploit, password-adjacent work), reach for SHA-256 or better.

Neither is for passwords

Both SHA-1 and SHA-256 are fast, which is exactly wrong for passwords — see why you should never use MD5 (or fast hashes) for passwords. Use bcrypt, scrypt, or Argon2 there.

Generate a hash

Try the hash generator to compute SHA-1, SHA-256, and MD5 for any text in your browser, and compare with MD5 vs SHA-256.