๐งฎ Checksum Calculator
Calculate the CRC32 and Adler-32 checksums of any text on the spot. Useful for verifying file-transfer integrity concepts or learning how checksum algorithms work. All calculation happens entirely in your browser.
How to use
- Enter the text you want to checksum.
- The CRC32 and Adler-32 checksums (in hex) are shown automatically.
How the calculation works
A checksum is a short value used to detect errors โ flipped bits and the like โ introduced while data is transmitted or stored. Sender and receiver compute the same value and check that they match. CRC32 (cyclic redundancy check) treats the data as a polynomial and takes the 32-bit remainder after division by a fixed generator polynomial. This tool uses the standard CRC-32 found in ZIP, PNG and Ethernet (generator polynomial 0x04C11DB7, computed in its bit-reversed form 0xEDB88320). It is particularly good at catching bursts of consecutive bit errors. Adler-32, used in zlib compression, combines two running sums modulo 65521 (the largest prime below 65536): A, the sum of the byte values, and B, the sum of the successive values of A. It is fast to compute but detects errors less reliably than CRC32 on short data.
Worked example
CRC32 of "hello": 3610a686 The CRC32 of "The quick brown fox jumps over the lazy dog" is 414fa339 โ the classic test value for checking a CRC32 implementation. The Adler-32 of "Wikipedia" is 11e60398. Change a single character and the value changes, so comparing values before and after copying data confirms it arrived intact.
Things to be aware of
- CRC32 and Adler-32 catch accidental errors. They are trivial to forge deliberately, so they are no use for security.
- Input text is processed as UTF-8 bytes; a different encoding gives a different value.
- Differences in line endings (LF versus CR+LF) or trailing spaces also change the value.
- For tamper detection, use a cryptographic hash such as SHA-256.
FAQ
What's the difference between CRC32 and Adler-32?
Both are checksum algorithms used for error detection. CRC32 is commonly used in ZIP files, while Adler-32 (used in zlib compression) is faster to compute but offers somewhat weaker error detection.
Can this checksum an actual file?
No โ this tool only checksums text input. To hash a file, try our Hash Generator.
Can I use this as a security hash?
No. CRC32 and Adler-32 are error-detection checksums, not cryptographically secure hash functions. Use something like SHA-256 for security purposes.