CRC32 Calculator
Calculate the CRC-32/ISO-HDLC checksum of text or hex bytes. Nothing is uploaded — the calculation is local.
CRC32
CRC-32 is a checksum used to detect accidental changes to data — it appears in zip, gzip and PNG. It is not a cryptographic hash and must not be used for security. Different CRC implementations use different parameters, which is why results can differ between sources; this tool fixes the parameters so the output is reproducible.
Parameters used
- Variant: CRC-32/ISO-HDLC (IEEE 802.3).
- Poly 0xEDB88320, init 0xFFFFFFFF, xorout 0xFFFFFFFF.
- Text is UTF-8 encoded before checksumming.
Frequently asked questions
Which CRC-32 variant does this use?
CRC-32/ISO-HDLC (IEEE 802.3): polynomial 0xEDB88320, initial value 0xFFFFFFFF, final XOR 0xFFFFFFFF — the variant used by zip, gzip and PNG.
Is CRC-32 the same as a hash?
No. CRC-32 is a checksum for detecting accidental corruption, not a cryptographic hash, and it is not suitable for security.
Can I paste hex bytes?
Yes. Switch the input to hex and paste bytes separated by spaces or commas, with or without 0x prefixes.
Does it handle text correctly?
Yes. Text is encoded as UTF-8 before the checksum is calculated, so accented and non-Latin characters are handled.
Why does another tool give a different value?
Different CRC parameters (poly, init, refin/refout, xorout) give different results. This tool states exactly which parameters it uses.
Is my input sent anywhere?
No. The checksum is calculated locally in your browser.
Related: the chmod calculator and query string parser, or browse every browser-only tool on the all tools page.