What is a cryptographic hash?

A hash function maps input data to a fixed-length digest. Small input changes produce very different outputs, which makes hashes useful for integrity checks and blockchain identifiers.

Which hash algorithm should I use?

SHA-256 is a common general-purpose choice. Keccak-256 is used heavily in Ethereum. MD5 and SHA-1 are legacy—fine for non-security checksums, but not for modern cryptographic security.

Can I reverse a hash to get the original text?

No. Cryptographic hashes are one-way. You can only compare digests or brute-force likely inputs. Never store passwords as plain hashes without a proper password-hashing scheme.

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SHA-256 Hash Generator

Generate cryptographic hashes using SHA-256, SHA-512, Keccak-256 (Ethereum), and more. Hash text or files securely in your browser.

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Hash Algorithms in Blockchain

SHA-256

The backbone of Bitcoin. Used for mining (proof-of-work), transaction IDs, and Merkle trees. Produces a 256-bit (32-byte) hash.

Keccak-256

Ethereum's hash function. Used for addresses, transaction hashes, and smart contract storage. Not the same as SHA-3 despite similar origins.

SHA-512

Extended security with 512-bit output. Used in some wallet derivation paths (BIP-32) and for extra security margins.

MD5 / SHA-1

Legacy algorithms. Not secure for cryptographic use but still common for checksums and non-security applications like Git commit IDs.

FAQ

What is a cryptographic hash?: A hash function maps input data to a fixed-length digest. Small input changes produce very different outputs, which makes hashes useful for integrity checks and blockchain identifiers.
Which hash algorithm should I use?: SHA-256 is a common general-purpose choice. Keccak-256 is used heavily in Ethereum. MD5 and SHA-1 are legacy—fine for non-security checksums, but not for modern cryptographic security.
Can I reverse a hash to get the original text?: No. Cryptographic hashes are one-way. You can only compare digests or brute-force likely inputs. Never store passwords as plain hashes without a proper password-hashing scheme.