SHA-256 File Checksum Calculator

SHA-256 (Secure Hash Algorithm 256-bit) is a cryptographic hash function that produces a fixed 64-character hexadecimal digest from any input. It is used for file checksums because even a single-bit change in the input produces a completely different output — making it ideal for verifying file integrity. If the SHA-256 hash of a downloaded file matches the one published by the author, you can be confident the file has not been tampered with or corrupted in transit.

MD5 was broken in 2004 when researchers demonstrated collision attacks — meaning two different inputs can produce the same MD5 hash. This makes MD5 unsuitable for security-sensitive uses like verifying software downloads or signing certificates. SHA-256 belongs to the SHA-2 family and has no known practical collision vulnerabilities. For integrity verification of files, always prefer SHA-256 (or SHA-512). MD5 may still appear in legacy systems or non-security contexts like cache keys, but should never be used for trust verification.

The Web Crypto API (window.crypto.subtle) is a browser-native cryptography interface. To compute SHA-256, you call crypto.subtle.digest('SHA-256', data) where data is an ArrayBuffer. This returns a Promise that resolves to an ArrayBuffer containing the raw hash bytes. You then convert those bytes to a hex string using a Uint8Array and Array.from(). The entire operation runs inside the browser — no data ever leaves your device. This tool uses that exact approach with async/await for clarity.

Yes. Download your file, then either paste its text content into the textarea or upload it using the file picker. The tool will compute its SHA-256 hash. Compare that hash to the checksum published by the software author (often listed as a .sha256 file or on the release page). If the hashes match exactly (case-insensitive), the file is intact. If they differ by even one character, the file may have been corrupted or modified and should not be trusted.