CRC32 Generator
Calculate the CRC32 checksum of any text instantly. The tool encodes your input as UTF-8 and applies the standard IEEE 802.3 CRC-32 polynomial used by ZIP, gzip, PNG and Ethernet, then returns the value as eight hex digits or as an unsigned decimal number. Use it to check stored checksums, debug file formats and compare results with zlib, PHP crc32 or other libraries.
Frequently asked questions
What is CRC32?
CRC32 is a 32-bit cyclic redundancy check that detects accidental changes to data. This tool uses the IEEE 802.3 polynomial 0x04C11DB7 in reflected form, the variant used by ZIP, gzip, PNG and zlib. The result is a single 32-bit number.
What are the standard CRC32 check values?
The text 123456789 gives cbf43926, the published check value for CRC-32. Empty input gives 00000000 and abc gives 352441c2. You can use these to confirm that another implementation uses the same variant.
Why do some tools show a different CRC32?
Other variants exist, such as CRC-32C (Castagnoli) used by iSCSI and ext4, or the non-reflected BZIP2 form. They use different polynomials or bit orders and give different values. Also check that both sides hash the same bytes, including line breaks.
What does the decimal output mean?
Decimal shows the checksum as an unsigned integer from 0 to 4294967295. This matches PHP's crc32 on 64-bit systems and Python's zlib.crc32. The hex output is the same number written as eight hexadecimal digits.
Is CRC32 a cryptographic hash?
No. CRC32 detects random transmission errors, but anyone can craft data with a chosen checksum. Use SHA-256 or another cryptographic hash when you need protection against deliberate tampering.
How likely are CRC32 collisions?
With only 32 bits, two random inputs share a checksum with a probability of about one in four billion. Among about 77,000 inputs, the chance that some pair collides already reaches 50 percent. CRC32 is fine for error detection but not for unique identifiers.
How is my text converted before the checksum?
The tool takes the UTF-8 bytes of the text exactly as entered. Non-ASCII characters take several bytes, and line breaks count, so make sure the other side uses the same bytes.
Is the hex output padded?
Yes. The hex form always has eight lowercase digits, with leading zeros where needed, so 0x0000abcd appears as 0000abcd. Some tools drop leading zeros or print uppercase, which is the same value.
Can I compute the CRC32 of a file?
This tool works on text you paste. For files, use a local command such as crc32 from the libarchive tools or a short script with zlib. The ZIP central directory also stores the CRC32 of each entry.
How long can the input be?
Up to 5 MiB of text per request. CRC32 is very fast, so the result returns immediately, and the input is not stored.