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Adler32 Calculator
Compute an Adler-32 checksum from text or a file and watch the A and B accumulators build up.
Compute an Adler-32 checksum
Adler-32: —
Decimal: —
A accumulator: —
B accumulator: —
Bytes processed: —
How to use the Adler32 Calculator
- Type the text you want to checksum, or choose a file to read.
- Click compute to run the hand written Adler-32 routine.
- Read the checksum, then the A and B accumulators and the byte steps.
Features
- Text or file input
- Hand written Adler-32 implementation
- A and B accumulator values
- Step table with the modulo reduction
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Frequently Asked Questions
Common questions about the free online adler32 calculator.
Adler-32 is a fast checksum that keeps two running sums of the input bytes and combines them
into a single thirty two bit value.
A starts at one and gains each byte value, B starts at zero and gains the current value of A,
and both are reduced modulo 65521 after every byte.
It is the largest prime number below 65536, which keeps the arithmetic inside thirty two bit
integers while giving good mixing.
The final value is B multiplied by 65536 plus A, written as eight hexadecimal digits so it is
easy to compare.
No. Both detect accidental corruption, but CRC32 has stronger error detection properties
while Adler-32 is usually faster in software.
No. A checksum is not a cryptographic hash, so use a dedicated hash such as SHA-256 for
anything security related.
Choose a file with the picker. The tool reads it in your browser and shows the checksum and
the byte count without uploading anything.
The value should match any correct Adler-32 implementation. Differences usually come from
newline conversion or from hashing the wrong bytes.
No. Everything is processed locally in your browser and the file never leaves your device.
Last updated: October 10, 2026