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About this tool
Compute the CRC32 checksum of text as a hex value.
The CRC32 Calculator computes the CRC-32 checksum of text using the standard IEEE 802.3 variant — reversed polynomial 0xEDB88320, initial value 0xFFFFFFFF, final XOR of 0xFFFFFFFF — the same algorithm used by zip, gzip and PNG. It returns the 32-bit result as eight hex digits, as an unsigned decimal, and reports the input length, so "hello world" gives 0x0d4a1185. It is for developers verifying a checksum by hand rather than trusting a value copied out of a log.
Open CRC32 Calculator on AltFTool — it loads instantly in your browser.
Type or paste text into the Text box, which starts with hello world; case and trailing spaces change the checksum, while non-ASCII text may differ from UTF-8 CRC32 tools because this calculator uses each JavaScript character code's low byte
Read the Result line as you type; it shows the checksum as eight lowercase hex digits behind a 0x prefix, with Decimal and Length tiles below it
Press Copy to place the input and checksum summary on your clipboard, or Download to save it as crc32-calculator.txt
Polynomial 0xEDB88320 reflected, init and final XOR 0xFFFFFFFF — the one zip, gzip and PNG use, so values match those tools.
Some APIs report CRC32 as a signed or unsigned integer rather than hex; both forms are shown so you can compare either way.
A mismatch is often a stray trailing newline or space, and the length makes that visible immediately.
CRC-32/ISO-HDLC, commonly called CRC-32 or IEEE 802.3 — reflected polynomial 0xEDB88320 (equivalent to 0x04C11DB7 unreflected), initial value 0xFFFFFFFF, and a final XOR with 0xFFFFFFFF. Its standard check value for the string "123456789" is 0xCBF43926, which is what this tool returns.
No. CRC32 is an error-detection code with only 32 bits, so collisions can be constructed deliberately in moments and are expected by chance after roughly 2^16 (about 65,000) random inputs. Use it to catch accidental corruption; use SHA-256 when the concern is tampering.
Usually the bytes differ, not the algorithm. The most common causes are a trailing newline, CRLF versus LF line endings, and non-ASCII characters — this tool hashes each character's code unit, so text outside ASCII will not match a CRC32 taken over UTF-8 bytes. Check the reported character count first.
0 to 4,294,967,295 (2^32 - 1), always shown here as exactly eight hex digits with leading zeros preserved. Some languages print it as a signed 32-bit integer instead, which is why you may see a negative number for the same checksum elsewhere.
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