CRC-32 & CRC-32C

Client

Two common 32-bit cyclic redundancy checks: CRC-32 (IEEE) as in PNG, ZIP, and many Ethernet FCS descriptions, and CRC-32C (Castagnoli) used in iSCSI, SCTP, and some storage stacks. Paste UTF-8 or raw hex bytes—both values update instantly.

Related tools

For full-file SHA and MD5 alongside CRC-32, use file checksum. To edit bytes as text, pair with the hex encoder.

Local only: CRCs run on bytes in this tab—UTF-8 for text mode, raw nibbles for hex mode (same as PNG/ZIP CRC-32 and CRC-32C / Castagnoli used by iSCSI and protobuf).
Input
?

IEEE CRC-32 matches ZIP, PNG, and Ethernet FCS family (polynomial 0xEDB88320 reflected). CRC-32C uses Castagnoli 0x82F63B78 reflected—do not mix them when comparing to a spec.

CRC-32 (IEEE)

Hex
0x00000000
Decimal (uint32)
0
Lowercase unprefixed
00000000

CRC-32C (Castagnoli)

Hex
0x00000000
Decimal (uint32)
0
Lowercase unprefixed
00000000

Common use cases

  • Sanity-check a short wire payload or frame when docs cite IEEE CRC-32 versus CRC-32C.
  • Compare against file checksum output: the file tool also lists CRC-32 for whole-file bytes.
  • Debug hex dumps from firmware or logs by pasting nibbles in hex mode.
  • Teach why different polynomials yield different fingerprints on the same bytes.

Common mistakes to avoid

  • Mixing CRC-32 with CRC-32C

    They use different polynomials—only one will match your spec. Confirm which variant your format or chip documents.

  • Expecting the same value after newline changes

    CRC is over raw bytes; CRLF vs LF or a trailing space changes the digest.

  • Using this for cryptographic integrity

    CRCs detect accidents, not attackers—use SHA-256 or similar when adversaries matter.

FAQ

Why is empty input zero?

Both implementations use the usual init/xorout pattern for these polynomials, which yields 0 for an empty byte sequence.

Can I prefill text?

Yes—?q= or ?qb= fills the UTF-8 textarea.

Big-endian vs little-endian display?

The hex value is the 32-bit residue as a single unsigned integer in the usual big-endian hex print (MSB first).

Common search terms

Phrases people search for that match this tool. See the full long-tail keyword index.

  • crc32 calculator online browser
  • crc32c castagnoli utf8 hex bytes
  • ieee crc32 vs crc32c difference zip png
  • calculate crc32 from hex string local

More tools

Related utilities you can open in another tab—mostly client-side.