Compute Adler-32 checksums

Compute an Adler-32 value for lightweight stream corruption detection.

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ToolAdler-32 Checksum
Input
Output
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How it works

Two 16-bit sums update for each byte: s1 accumulates values and s2 accumulates s1; both are reduced modulo 65521 and packed into the final value. It is fast but weaker than CRC-32 for some short or patterned inputs.

  • The prime modulus keeps arithmetic simple.
  • Adler-32 is not cryptographic integrity.

Worked example

Checksum Text
Compute the Adler-32 checksum of a simple string
Input
											Hello, World!
Output
												1f9e046a

When to use this

zlib streams, lightweight transfers, and compressed-block tests use Adler-32 values.

Edge cases

  • Short messages can have weaker detection than CRC-32.
  • Packed byte order changes displayed hexadecimal.
  • An attacker can recompute the value after modifying data.

References