🔢 CRC-32 & Adler-32 Checksum Calculator
Type text or drop a file to get its CRC-32 (the ZIP/PNG checksum) and Adler-32 (zlib) values in hex and decimal.
CRC-32 (ZIP/PNG)
414FA339
decimal 1,095,738,169
Adler-32 (zlib)
5BDC0FDA
decimal 1,541,148,634
43 bytes checksummed
CRC-32 and Adler-32 are fast, non-cryptographic checksums used to detect accidental corruption, CRC-32 is the one inside ZIP archives and PNG chunks; Adler-32 is used by zlib. They quickly tell you whether two copies of some data are byte-identical. They are NOT for security or passwords (they're easy to forge on purpose and can collide), use SHA-256 for that. 🔒 Computed entirely in your browser.
How the crc-32 & adler-32 checksum calculator works
CRC-32 and Adler-32 are fast, non-cryptographic checksums that condense any amount of data into a single 32-bit fingerprint used to detect accidental corruption. CRC-32 (the ISO-HDLC variant) is the exact checksum stored inside ZIP archive entries and PNG chunks, so it is the one to match when validating those formats; Adler-32 is the lighter checksum zlib uses. This tool reads your text as UTF-8 bytes (or reads a file locally), runs both algorithms, and reports each result in uppercase hex and decimal. If two copies of a file produce the same CRC-32, they are byte-identical.
These are integrity checksums, not security hashes: they are excellent at catching random corruption from a bad transfer or disk error, but they are trivial to forge deliberately and different inputs can be made to collide, so never use them to verify authenticity or store passwords, use SHA-256 for that. The standard CRC-32 check value for the ASCII string "123456789" is CBF43926, which you can use to confirm the implementation. Text is hashed as UTF-8, so accented characters count as multiple bytes. Everything runs in your browser; files are never uploaded.
Frequently asked questions
What is a CRC-32 checksum used for?
To detect accidental changes to data. ZIP archives and PNG images store a CRC-32 of their contents so software can confirm nothing got corrupted in transit or on disk. Recomputing the CRC-32 and comparing it to the stored value tells you whether the data is intact.
What is the difference between CRC-32 and Adler-32?
Both are 32-bit integrity checksums, but CRC-32 is a cyclic redundancy check (used by ZIP and PNG) while Adler-32 is a simpler running-sum checksum used by zlib. Adler-32 is a touch faster to compute but slightly weaker at catching short errors; this tool shows both.
Can I use CRC-32 to check a password or for security?
No. CRC-32 and Adler-32 are not cryptographic. They are easy to reverse and to collide on purpose, so they offer no security. Use them only to catch accidental corruption; for passwords or authenticity, use a cryptographic hash like SHA-256.
How do I verify two files are identical?
Compute the CRC-32 of each file and compare. Matching CRC-32 values mean the files are almost certainly identical; for absolute certainty against deliberate tampering, compare a cryptographic hash instead.
What is the CRC-32 of "123456789"?
CBF43926. That is the standard published check value for the CRC-32/ISO-HDLC algorithm, so you can type that string to confirm the calculator matches the reference.
Is my file uploaded to compute the checksum?
No, the file is read and checksummed entirely in your browser, so nothing leaves your device and it works offline.