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Checksum calculator

Did the download arrive intact? Are two files really the same? You calculate SHA-256, MD5 and more right here on your device, large files too.

0 bytes as UTF-8. Every line break counts as one character (LF).

Upper and lower case, spaces and colons do not matter. A whole line from a .sha256 or .md5 file works too. The tool recognizes which checksum is meant by its length.

Which checksums

For text and normal files, everything is done at once. Above a certain size, this tool calculates everything itself, the SHA values too; the size depends on your device’s memory. Then it is worth leaving on only the checksum you really need.

MD5 and SHA-1: good against errors, not against intentMD5 and SHA-1 reliably show whether a bit flipped during download. That is enough for this, and many providers still show them. But it has long been known how to build two different files with the same MD5 (since 2004) or SHA-1 (since 2017). If you want to be sure nobody swapped the file on the way, you need SHA-256 or longer. CRC-32 is not a security function at all, just the small error check from ZIP files.

More for text: Compare texts · Count characters and words

Text and files stay on this device. The calculating happens here, nothing is sent.

How it works
  1. 01Type text or choose a file. The checksums appear right away, with a progress bar for large files.
  2. 02Paste the expected checksum from the download page. Green means: it matches. Red means: it differs, so better download again.
  3. 03“Two files” checks whether two files are really the same, byte for byte.

A checksum is a short fingerprint of a file: If even one bit changes, a completely different sum comes out. If your sum matches the provider’s, you have exactly the file they mean. Whether the provider itself can be trusted, no checksum can tell.

SHA-1, SHA-256, SHA-384 and SHA-512 are calculated by the browser itself (through crypto.subtle, built in and fast). It cannot do MD5 and CRC-32, so this tool calculates those with its own code, checked against the standards. Files are read in small pieces. For the browser to calculate the SHA values, though, the file has to sit in memory in one piece, and while it calculates, briefly even twice. That is why the tool does this only up to a limit that depends on the device: 256 MB if the browser does not reveal its memory (Firefox, Safari), otherwise one sixteenth of it and never more than 512 MB. Larger files go through the tool itself piece by piece, the SHA values too. That takes noticeably longer, with all six checksums on a laptop roughly one minute per two gigabytes; with only SHA-256 about ten times faster.

Text is calculated as UTF-8, every line break as one character (LF). If you want to check a text file, use the “File” tab: A file from Windows may store line breaks as two characters (CRLF), and then the pasted text gives a different sum than the file. The address contains only the tab, for example bnkz.de/en/text/checksum/#datei. Neither text nor checksums end up there.