Calculate CRC32 checksums for text and files using standard and Castagnoli polynomial implementations.
CRC32 Calculator produces 32-bit cyclic redundancy checks for entered text and local files. It reports conventional CRC-32 and CRC-32C, which uses the Castagnoli polynomial. This helps when a protocol, archive, or checksum listing specifies either variant. File contents are processed entirely in the browser and are not uploaded. A frequent mistake is treating CRC32 as one universal calculation: CRC-32 and CRC-32C use different polynomials and generally produce different checksums for the same bytes.
A concrete input and expected output from the current implementation.
Input
123456789
Expected output
CRC-32: CBF43926 CRC-32C: E3069283
These nine ASCII digits are a standard check sequence for both variants. Conventional CRC-32 produces 0xCBF43926, while CRC-32C with the Castagnoli polynomial produces 0xE3069283.
The standard CRC-32 calculation uses the polynomial represented as 0x04C11DB7. CRC-32C uses the Castagnoli polynomial, represented as 0x1EDC6F41. Each calculation reduces the input byte sequence to a 32-bit remainder, normally shown as eight hexadecimal digits. Because the polynomial is part of the checksum definition, the two results are not interchangeable.
The selected calculation processes every input byte in order. Repeating it with the same bytes and CRC variant produces the same 32-bit value. A changed character, line ending, byte-order mark, or trailing newline can change the checksum. In file mode, the checksum covers the file contents rather than its name or filesystem metadata.
First confirm that both calculators use the same variant. CRC-32 and CRC-32C have different polynomials. Also compare the exact input bytes, including text encoding, capitalization, spaces, and final newline characters. If a binary format stores the checksum in little-endian order, its byte sequence may appear reversed relative to the displayed hexadecimal value.
No. A CRC is designed to detect accidental transmission or storage errors, not deliberate modification. Its 32-bit output permits collisions, and an attacker can construct changes that preserve or replace a CRC. Use a cryptographic hash or an authenticated mechanism when tamper resistance, identity, or security is required.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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