Verify File Checksums & SHA Hashes in Browser Calculate and verify file checksums using SHA algorithms.

Under the hood, it works by using the Web Crypto API's subtle.digest() function to generate a checksum for a given file. This process starts when a user selects a file and an algorithm such as SHA-256, which produces a 32-byte or 64-character hexadecimal hash. The tool reads the selected file into memory as an ArrayBuffer, then passes this data to subtle.digest(), along with the chosen algorithm. The resulting digest is a unique digital fingerprint that can be used for integrity verification.

The avalanche effect inherent in SHA algorithms ensures that even small changes to the input file produce drastically different hashes, making it suitable for detecting accidental or malicious modifications. When comparing against an expected checksum value, the tool converts both the generated and expected hashes to lowercase before performing a string comparison, ensuring case-insensitivity. This process allows users to verify whether their files have been tampered with during transmission or storage.

The React library is used to manage state changes within the application, such as updating the displayed hash when the algorithm or file is changed. The useState hook maintains variables like algo and expected, while useCallback handles asynchronous operations like generating the checksum from a file's ArrayBuffer and copying it to the clipboard using functions from the @/lib/utils module. Array manipulation techniques are also employed to convert the resulting digest into a hexadecimal string representation of the hash.

It utilizes specific technologies including React for state management and user interface updates, Web Crypto API for cryptographic operations like generating digests, and JavaScript's built-in array methods to process binary data as hexadecimal strings. This combination enables efficient and secure checksum generation directly within the browser without requiring file uploads or external servers, making it a useful tool in scenarios where file integrity must be verified locally.