CRC-32 Calculator

This online CRC-32 calculator computes CRC-32 checksums for text, files, or URLs. It uses CRC-32/ISO-HDLC by default and supports other CRC-32 models and input encodings. Expand to read more.

What is CRC-32?

CRC-32 is a family of cyclic redundancy check algorithms that produces a 32-bit checksum. It is widely used to detect accidental changes in files, archives, network frames, and other binary data. CRC-32 is not a single algorithm: models with different parameters can return different checksums for the same input.

This calculator uses CRC-32/ISO-HDLC by default. This widely recognized model is also known as CRC-32, CRC-32/ADCCP, CRC-32/V-42, CRC-32/XZ, or PKZIP.

CRC-32/ISO-HDLC parameters

  • Width: 32
  • Polynomial: 04C11DB7
  • Initial value: FFFFFFFF
  • Reflect input: true
  • Reflect output: true
  • Final XOR value: FFFFFFFF
  • Check value for ASCII 123456789: CBF43926

These parameters and aliases follow the CRC RevEng catalogue. The check value is useful for confirming that another implementation uses the same model and parameters.

How to calculate a CRC-32 checksum

Enter text, upload a file, or provide a URL. Choose the input encoding and the CRC-32 model required by your file format or protocol, then select Calculate. The file and URL modes calculate the checksum from the input bytes rather than from a displayed hexadecimal value.

Which CRC-32 model should I choose?

Use the model named by the file format, protocol, device, or application you need to match. The same input will not necessarily produce the same result under different CRC-32 models.

Common choices available here include:

  • CRC-32/ISO-HDLC for specifications that call for standard CRC-32, PKZIP, CRC-32/ADCCP, or the CBF43926 check value.
  • CRC-32/ISCSI for specifications that name CRC-32C or Castagnoli.
  • CRC-32/CKSUM when matching the POSIX cksum model.
  • CRC-32/BZIP2, CRC-32/MPEG-2, and CRC-32/JAMCRC when those variants are explicitly required.

If you need another checksum width or custom parameters, use the general CRC calculator. For a 16-bit result, use the CRC-16 calculator.

CRC-32 FAQ

Is CRC-32 a cryptographic hash?

No. CRC-32 is intended to detect accidental corruption and does not protect data against intentional modification. Use a cryptographic hash or an authenticated integrity mechanism when security is required.

Is CRC-32 the same as CRC-32C?

No. CRC-32C commonly refers to the Castagnoli model listed here as CRC-32/ISCSI. It uses a different polynomial from CRC-32/ISO-HDLC and normally produces a different checksum for the same input.

Why does another CRC-32 calculator return a different result?

Check that both tools use the same model, input bytes, input encoding, and output format. If the model name is unclear, compare its polynomial, initial value, reflection settings, final XOR value, and the 123456789 check value.

How many hexadecimal digits are in a CRC-32 value?

A 32-bit result is normally written as eight hexadecimal digits, from 00000000 through FFFFFFFF. Leading zeroes are significant when displaying the complete checksum width.

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