File Checksum (CRC32)

How to use

1. Choose a file with the file picker.
2. While “Calculating…” is shown, the file is read and its CRC32 is computed in the background.
3. The result line shows the file name, its size in bytes and the CRC32 as 8 hexadecimal digits.
4. Use the copy button to copy the CRC32 value and compare it with the one you expect, for example from a ZIP listing or an .sfv file. Upper or lower case does not matter.
5. Choose another file to calculate again.

Frequently asked questions

Is my file uploaded?

No. The file is read and processed only in your browser.

What can I use a CRC32 checksum for?

Checking that a file was not accidentally corrupted while downloading, copying or transferring it. This is the standard CRC-32 used by ZIP, gzip and PNG, so a matching value means the file is almost certainly intact.

Does a matching CRC32 prove the file was not tampered with?

No. A file can be deliberately altered to produce any CRC32 value, and with only 32 bits, different files can share the same one. To detect tampering, compare a SHA-256 hash instead.

Why does another program show a different CRC32?

It may use another variant, such as CRC-32C (Castagnoli), or show the value in decimal instead of hex. This tool uses the standard CRC-32 (IEEE 802.3, polynomial 0x04C11DB7) and shows it as 8 lowercase hex digits.

Is there a file size limit?

There is no fixed limit, but the whole file is read into memory and then copied into 32-bit WebAssembly memory (at most 4 GB), so it needs about twice the file's size in memory. Files of several gigabytes, or smaller ones on devices with little memory, may fail.