Adler-32

Adler-32 is a 32-bit checksum designed by Mark Adler; faster to compute than CRC32 but slightly weaker at error detection, used for zlib compression stream integrity.

Purpose

Provides a checksum faster than CRC32 for performance-sensitive compression stream integrity verification.

Mechanism

A = 1 + Σd_i (mod 65521), B = Σ(1 + Σ_{j≤i} d_j) (mod 65521), output B<<16 | A. The modulus 65521 (largest prime below 65536) ensures good distribution.

Use cases

zlib/gzip stream verification
PNG IDAT checksums
Real-time compression integrity
Low-overhead checksum scenarios

Examples

Input
```
hello
```
Output
```
0x062c0215
```
Slightly weaker than CRC32 but faster

Common errors

Adler-32 error-detection degrades significantly on short inputs: Use CRC32 for short data

Related terms

CRC32 is a 32-bit cyclic redundancy check based on polynomial division over GF(2), used to detect transmission errors — not a cryptographic hash.

MD5 is a 128-bit cryptographic hash function designed by Ronald Rivest; proven insecure by collision attacks, it is now used only for non-security purposes such as checksums.

Related tools

Hash Calculator

Compute MD5, SHA-1, SHA-256, or SHA-512 hashes with hex or Base64 output. Free, private, and 100% client-side.

Adler32 — pure client-side tool. Privacy-first, no server round-trip.

References