Adler 32 Checksum Calculator
Compute an unsigned Adler-32 checksum from exact UTF-8 text or hexadecimal bytes and inspect the running sums.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Initialize the two modular sums and update both once for each input byte. Combine the final sums into a 32-bit unsigned number and network-order hexadecimal bytes.
s1=(s1+byte) mod 65521; s2=(s2+s1) mod 65521; checksum=s2×65536+s1
Worked example
UTF-8 text Wikipedia has Adler-32 0x11E60398 (decimal 300286872). Empty input produces 0x00000001.
Assumptions and input details
No Unicode normalization, newline transformation or byte-order mark is added. Hex mode accepts complete pairs and whitespace only. Limits: 20000 text code units or 60000 bytes; the running table shows the first 199 byte updates and the last, with omitted count. Adler-32 is an accidental-error checksum, not cryptographic protection, authenticity or a unique fingerprint.
References: IETF RFC 1950: Adler-32 definition
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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