What is a CRC checksum?
A cyclic redundancy check catches accidental corruption in transmitted data. Two calculators disagree unless every parameter, not just the polynomial, matches.
What CRC is designed to do
A cyclic redundancy check is an error-detection value calculated from a sequence of bits or bytes. A sender appends the CRC to a message, and a receiver calculates the same model again to determine whether the data changed in transit or storage.
CRC is excellent at detecting common transmission errors, including single-bit changes and many burst errors. It is not a cryptographic hash and should not be used to prove authenticity or protect against deliberate modification.
Why two CRC calculators can disagree
The polynomial alone does not identify a complete CRC model. Width, initial value, input reflection, output reflection, final XOR, input encoding, and byte order must also match.
When comparing tools, first test the standard ASCII string 123456789. Published CRC models normally include a check value for this exact input.
The complete parameter set
A named CRC model is a bundle of parameters rather than a single polynomial.
- Width
- Polynomial
- Initial value
- RefIn
- RefOut
- XorOut
- Check value
- Residue
Apply this reference
Change CRC parameters and compare standard algorithm results using the browser-based calculator.