BRev SHA-256 hash generator
SHA-256 produces a 256-bit digest — 64 hexadecimal characters — and is the member of the SHA-2 family that has become the internet’s default. TLS certificates, code signing, package managers, Bitcoin, JWT’s HS256 and almost every “verify this download” instruction written in the last decade use it. Unlike MD5 and SHA-1 it has no practical collision or preimage attack, and none is expected.
Verifying a download is its most common use, and the mechanics are worth stating exactly. On macOS: shasum -a 256 file. On Linux: sha256sum file. On Windows PowerShell: Get-FileHash file -Algorithm SHA256. Compare the result to the published value — the tool on this page does the same for a dropped file, computing entirely on your device, which matters when the file is large or confidential.
What a checksum proves is narrower than people assume: that the bytes you have are the bytes whose digest was published. If an attacker replaced both the file and the checksum on the same page, they match perfectly. A checksum defends against corrupted downloads, truncation and a compromised mirror when the checksum came from elsewhere — a GPG-signed manifest, or the vendor’s own site rather than the mirror’s. That signature, not the hash, is what makes it trustworthy.
SHA-256 in numbers
| Property | Value |
|---|---|
| Output | 256 bits — 64 hex characters |
| Block size | 512 bits |
| Published | 2001 (NSA/NIST), FIPS 180-2 — part of the SHA-2 family |
| Collision resistance | No practical attack known |
| Preimage resistance | No practical attack known |
Is SHA-256 safe to use — and for what?
“Broken” and “fine” are both true of most hash functions depending on the job, so the answer is per use, not per algorithm.
| Use | Verdict | Why |
|---|---|---|
| Verifying downloads and release artefacts | Yes | The right default, and what nearly every project publishes. Pair it with a signature when the source itself could be compromised. |
| TLS certificates and code signing | Yes | The current standard across every CA and signing scheme. SHA-1 was removed from these uses precisely in favour of SHA-256. |
| HMAC and JWT signatures (HS256) | Yes | HMAC-SHA-256 is a keyed construction that remains secure even against hash weaknesses, and is the default for signed tokens and webhook verification. |
| Content addressing and deduplication | Yes | Collision-resistant against a deliberate attacker, which is what container registries and content-addressed stores need. |
| Password storage | No | Still the wrong tool, however strong the hash. SHA-256 is designed to be fast, so a GPU tries billions of candidates per second. Passwords need a slow, salted, memory-hard function: Argon2, scrypt or bcrypt. |
FAQ
How do I verify a download with SHA-256?
Compute the hash and compare it to the published value: shasum -a 256 file on macOS, sha256sum file on Linux, Get-FileHash file -Algorithm SHA256 in PowerShell. Or drop the file into the tool on this page, which computes it locally.
Is SHA-256 secure?
Yes — no practical collision or preimage attack exists, and it is the current standard for certificates, signing and content addressing. The one thing it is not suited to is password hashing, because it is deliberately fast.
What is the difference between SHA-256 and SHA-2?
SHA-2 is the family; SHA-256 is its 256-bit member, alongside SHA-224, SHA-384 and SHA-512. SHA-3 is a separate, newer family with a different internal design, not a replacement.