SHA-256 is a cryptographic hash function that turns any input into a fixed 256-bit fingerprint, written as 64 hexadecimal characters. Bitcoin uses it to link blocks and to run proof-of-work mining, which makes confirmed transactions very hard to change. Bitcoin Cash and Bitcoin SV also use it for mining.
How does SHA-256 work?
SHA-256 turns any input, from one word to a whole file, into a hash (or digest) that is always 256 bits long, written as 64 hexadecimal characters. It is a form of hashing, a core tool of cryptography. Three properties matter:
- Deterministic: the same input always gives the same hash.
- One-way: you cannot work back from a hash to its input, only guess and compare.
- Avalanche effect: change one character and the whole hash changes.
What does a SHA-256 hash look like?
Two words one capital letter apart, with hashes in groups of 16 characters:
- coinmama:
e925a5cad98a3533 3dcb4b8970c953ea 47acd0d2b9f9e4df 7397aad622994f5e - Coinmama:
e044e8a148719226 f7608fe1b4c30970 b4de7f699f4fddee 10d4bf34d23375a9
That one change flipped 130 of the 256 bits, about half, and neither hash gives a clue to the other.
How does Bitcoin use SHA-256?
Bitcoin usually runs SHA-256 twice, called double SHA-256 (SHA-256d), in four places:
- Mining: miners hash the block header over and over, changing a number called the nonce, until the result falls below the network’s target. This is proof of work, done today by ASIC miners. The difficulty adjustment moves the target.
- Linking blocks: each block header contains the previous block’s hash, so editing an old block changes every block after it.
- Transaction IDs: a TXID is the double SHA-256 hash of a transaction.
- Addresses: legacy addresses (starting with 1) hash the public key with SHA-256, then with RIPEMD-160.
Which coins use SHA-256?
As of September 2026, well-known coins mined with SHA-256 include:
- Bitcoin (BTC)
- Bitcoin Cash (BCH), which split from Bitcoin on 1 August 2017
- Bitcoin SV (BSV)
- Namecoin (NMC), which can be merge-mined with Bitcoin
The same ASIC machines mine all of them. Litecoin and Dogecoin use a different algorithm, Scrypt, and Ethereum stopped mining when it moved to proof of stake on 15 September 2022.
Why does SHA-256 matter when you buy crypto?
It makes Bitcoin’s history hard to rewrite. Changing a confirmed transaction would mean redoing the proof of work for its block and every block after it, which is why wallets and exchanges wait for confirmations. See the Bitcoin price and payment options.
Is SHA-256 secure?
Yes, by current standards. As of September 2026, NIST, the US standards body, lists SHA-256 as approved in its Secure Hash Standard (FIPS 180-4). It belongs to the SHA-2 family, designed by the US National Security Agency and first published by NIST in 2002.
Collisions (two inputs with the same hash) must exist in theory, but NIST rates finding one at about 2128 operations. Quantum computers might one day speed up guessing, though NIST still uses a SHA-256 collision search as a benchmark in its post-quantum security levels.
What are the risks and red flags?
- It does not protect your wallet. Your coins are only as safe as your private keys. Scams target people, not the hash: learn to spot phishing attacks.
- It is not a quality label. Using SHA-256 does not make a coin safer to buy, and cloud mining plans that promise fixed profits are a common scam sign: see mining scams.
Go deeper: What is proof of work? explains how mining secures a blockchain.
