Adler-32 Checksum Generator
Turn any text into its 8-character Adler-32 checksum instantly.
How to use the Adler-32 Checksum Generator
- Type or paste your text in the box.
- The Adler-32 checksum appears as you type.
- Click Copy to grab the result.
About the Adler-32 Checksum Generator
Adler-32 was designed by Mark Adler — co-author of zlib and gzip — as a checksum that would be cheaper to compute than CRC-32 while still catching the kinds of corruption that happen in practice. It is the integrity check carried by the zlib data format, so if you have ever decompressed a zlib stream, Adler-32 was quietly verifying it for you. The result is 32 bits, printed as 8 hexadecimal characters.
The trade was deliberate: Adler-32 is faster than CRC-32 but weaker. It works by keeping two running sums as it walks through the data and combining them, rather than doing polynomial division, which is why it is so cheap. The well-known weak spot is short messages — with only a few bytes of input the sums barely have room to spread out, so the checksums of short strings cluster together and a surprisingly small number of distinct values get used. For a few kilobytes of compressed data that hardly matters. For hashing a handful of short strings it matters a lot, and CRC-32 is the better pick.
Like every checksum on this page, Adler-32 is for accidents, not adversaries. It is fast precisely because it does nothing to resist someone who is actively trying to fool it, and constructing two different inputs with the same Adler-32 is easy. It answers “did this data arrive intact?” and nothing more. If the question is “did anyone tamper with this?”, you need a cryptographic hash such as SHA-256.
Frequently asked questions
Adler-32 or CRC-32 — which should I use?
Adler-32 is faster; CRC-32 is more reliable at spotting errors, especially on short data. If speed is not the bottleneck, CRC-32 is generally the safer default. Adler-32 shines on longer streams, which is exactly where zlib uses it.
Why is Adler-32 bad at short strings?
It builds its result from two running sums over the data. With only a few bytes those sums stay small, so short inputs only ever produce a narrow band of possible checksums and collisions become common.
Is Adler-32 secure?
No. It must never be used for passwords, signatures or anything an attacker might want to forge — producing two inputs with the same Adler-32 is trivial. It is a transmission-error check, nothing more.
Why is the result always 8 characters?
Adler-32 always produces 32 bits, and each hex character represents 4 bits, so the output is exactly 8 characters regardless of input size.
Is my text sent anywhere?
Your text is sent to our server to be checksummed, because browsers cannot compute Adler-32. It is processed and immediately discarded — never logged, never stored.