Which CRC-32 variant does this use?

It uses the standard IEEE 802.3 polynomial (reflected 0xEDB88820), initial value all-ones, and final XOR all-ones — the same CRC-32 used by ZIP, gzip, PNG, and Ethernet, so results match those formats and common libraries.

How can I check the result is correct?

The standard CRC check string is the ASCII text "123456789", which must produce 0xCBF43926. As another reference, the lowercase word "hello" produces 0x3495352B. Matching values confirm the implementation is correct.

Is CRC-32 a cryptographic hash?

No. CRC-32 is an error-detecting checksum designed to catch accidental corruption, not deliberate tampering. It is trivial to forge, so never use it for security, passwords, or integrity against an attacker — use SHA-256 or BLAKE3 for that.

Why is the decimal value shown as unsigned?

A CRC-32 is a 32-bit value. JavaScript bitwise operations are signed, so we mask with a right shift of zero to display the full unsigned 0 to 4294967295 range, matching what zip and gzip report.

What is the CRC-32 Checksum Calculator?

Free CRC-32 checksum calculator that computes the IEEE 802.3 CRC-32 (used by ZIP, PNG, gzip, and Ethernet) of text or raw hex bytes, in hex and decimal. Runs entirely in your browser in pure JavaScript; nothing is uploaded. It runs free in your browser on Gera Tools, with nothing uploaded.

CRC-32 Checksum Calculator

Name: CRC-32 Checksum Calculator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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This tool computes the CRC-32 checksum of any text or raw hex bytes and shows it in both hexadecimal and unsigned decimal, updating live as you type. CRC-32 is the error-detecting checksum built into common file formats and network frames, so it is ideal for verifying data integrity or matching a checksum produced by another tool.

How it works

The calculator uses the standard IEEE 802.3 polynomial (0xEDB88820) — the reflected form of 0x04C11DB7 — the same CRC-32 used by ZIP, gzip, PNG, and Ethernet. It precomputes a 256-entry lookup table, encodes your input to bytes, then runs the table-driven algorithm: starting from 0xFFFFFFFF, each byte updates the running value via crc = (crc >>> 8) XOR table[(crc XOR byte) & 0xFF], and the final value is XORed with 0xFFFFFFFF. This matches the output of standard CRC-32 libraries.

Reference check values

Input	CRC-32 (hex)
`123456789`	cbf43926
`hello`	3495352b
`The quick brown fox`	519025e9

The check string 123456789 producing 0xCBF43926 is the universal reference for the standard CRC-32 implementation. If your tool or library produces a different value for this string, you are either using a different variant or there is a bug.

Where CRC-32 is used and why it matters

CRC-32 is embedded in file formats and network protocols you interact with every day:

ZIP and gzip — each compressed entry stores a CRC-32 of the uncompressed data. Extraction software checks this value after decompression and reports corruption if they differ.
PNG — every chunk in a PNG file ends with a CRC-32 of the chunk type and data, allowing validation without loading the whole image.
Ethernet / IEEE 802.3 — network frames end with a 4-byte Frame Check Sequence computed with CRC-32. Network cards discard frames whose FCS does not match, silently preventing corrupt data from reaching software.

Knowing the CRC-32 of a specific input lets you verify a file arrived intact after transfer, reproduce a constant in a protocol implementation, or confirm a build artifact is bit-for-bit identical to a reference copy.

CRC-32 vs other checksums

CRC-32 detects all single-bit errors and all burst errors shorter than 32 bits, making it substantially more reliable than simple modular sums for data blocks up to several kilobytes. It is faster than MD5 or SHA-1 for pure integrity checking of non-security-sensitive data. However, CRC-32 is not a cryptographic hash — finding a collision intentionally is trivial, so never use it for passwords, digital signatures, or protecting against deliberate tampering. For those use cases, reach for SHA-256 or BLAKE3 instead.

Everything is computed in pure JavaScript in your browser; nothing is uploaded.