SHA-256 Hash Generator & File Checksum Calculator
Calculate SHA-1, SHA-256, and SHA-512 hashes for any file instantly. Drag and drop to verify file integrity by comparing checksums. Uses the Web Crypto API — your files are processed locally and never uploaded to any server.
Hash calculation runs entirely in your browser using the Web Crypto API. Your files are NEVER uploaded. Zero bytes leave your device. Verify in DevTools Network tab.
No size limit • All file types supported • Never uploaded
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Key Facts
- SHA-256 Output: Always produces a 64-character hexadecimal string (256 bits) regardless of input size
- Deterministic: The same file always produces the same hash. Even a 1-byte change creates a completely different result
- One-Way: You cannot reverse a hash to recover the original file. Hashes are fingerprints, not encryption
- Collision Resistant: No two different files have ever been found to produce the same SHA-256 hash
- Processing: Uses Web Crypto API (crypto.subtle.digest) — hardware-accelerated in modern browsers
- Privacy: Files are read into browser memory only. Zero network requests during hashing
SHA Algorithm Comparison
- SHA-1 (160-bit, 40 chars): Deprecated for security since 2017 due to practical collision attacks (Google SHAttered). Still used in Git commit hashes and legacy systems. Not recommended for integrity verification
- SHA-256 (256-bit, 64 chars): Current industry standard. Used in SSL/TLS certificates, Bitcoin blockchain, code signing, and file integrity verification. No known collisions. Recommended for all general purposes
- SHA-512 (512-bit, 128 chars): Longer hash with higher theoretical security margin. Slightly faster on 64-bit processors. Used when protocols specifically require it (e.g., certain HMAC implementations)
When to Use File Hashing
- Download Verification: Compare the hash of a downloaded file against the publisher's listed checksum to confirm it was not tampered with or corrupted during transfer
- Software Integrity: Verify that open-source software, drivers, or firmware images have not been modified by third parties
- Digital Forensics: Prove that evidence files have not been altered since collection. Hash values are admissible in court
- Backup Validation: Confirm that backed-up files are identical to originals by comparing their hashes
- Deduplication: Identify duplicate files across large datasets by comparing SHA-256 hashes instead of file contents
Frequently Asked Questions
What is a SHA-256 hash?
SHA-256 (Secure Hash Algorithm 256-bit) produces a unique 64-character hexadecimal fingerprint of any data. Even changing one byte in the input produces a completely different hash. It is used for file integrity verification, digital signatures, blockchain technology, and password storage.
Is my file uploaded to your server?
No. The file is processed entirely in your browser using the Web Crypto API (crypto.subtle.digest). It never leaves your device. You can verify by monitoring the Network tab in your browser developer tools during hashing — zero requests are made.
Which hash algorithm should I use?
SHA-256 is the standard choice for most purposes. SHA-1 is deprecated for security (practical collision attacks demonstrated in 2017) but still appears in legacy systems like Git. SHA-512 offers more bits but is rarely required unless specified by a protocol.
Can two different files have the same hash?
Theoretically possible (called a collision) but practically impossible for SHA-256. There are 2^256 possible hashes — a number larger than the estimated atoms in the observable universe. No SHA-256 collision has ever been found or demonstrated.
How long does hashing take for large files?
Small files (under 100 MB) are typically hashed in under a second. Files up to 1 GB take a few seconds depending on your device. The Web Crypto API uses hardware-accelerated hashing when available. Very large files may briefly make the tab unresponsive.