File SHA-256 Checksum Tool

This tool generates SHA256 checksum of a file to check if it was corrupted or altered. The checksum can also be used when sharing files. Processing is done in the browser, files are not uploaded.

This tool is fast, but processing of large files may take some time. For example, a 3GB file can take a minute or more to process, depending on your device. Processing time grows linearly with file size. Further details...

It's WASM, It's Fast

This page uses the WebAssembly (WASM) technology, which is faster than the same JavaScript code for computing the SHA256 hash. Modern browsers provide CryptoAPI functions that are faster than WASM, but they lack streaming processing. This means the file must be fully loaded into the browser's memory before processing, which can be a problem for large files. Therefore, the WASM option seems to be the best for computing the SHA-256 hash of files of different sizes in web applications.

Here are the results of performance tests for obtaining the SHA256 hash of a 100 MB (104,857,600 bytes) file.

Method	ms	bytes per ms
Windows 11, Intel Core i7-10700 CPU 2.90GHz (Desktop, 2020)
Edge CryptoAPI	465	225,500
Edge WASM	740	141,700
Edge Javascript	7,475	14,000
Firefox CryptoAPI	683	153,500
Firefox WASM	980	107,000
Firefox JavaScript	4,950	21,180
Powershell	302	347,200
VM Linux Mint	385	272,350
WSL Ubuntu	872	120,250
Windows 11, AMD Ryzen 9 7940HS 4.00 GHz (Mobile, 2023)
Edge WASM	540	194,100
Edge Javascript	4,760	22,000
Powershell	104	1,008,245
Android 14, Samsung Exynos 2400e 3.11 GHz (Phone, 2024)
Firefox WASM	1210	86,659
Chrome WASM	2400	43,690

You can use the command line to get the SHA-256 checksum.

Linux:

sha256sum <your_file>

Mac:

shasum -a 256 <your_file>

Windows Powershell:

Replace <your_file> with the path and name of the file you want to hash. Use quotes if the path or file name contains spaces.

Trivia

• The hash of an empty file is e3b0c44298fc1c149afbf4c8996fb92427ae​41e4649b934ca495991b7852b855. Though it may seem useless, it serves as a reference point in hashing algorithms.

• You can add the expected URL parameter when linking to this page.

• SHA-256 produces an output of 256 bits, so there are 2²⁵⁶ possible hash values. Obviously there are many more files; therefore collisions must exist. Still, no two distinct files have been found so far with the same SHA-256 hash, and the algorithm is considered secure against known collision attacks.