Checksum Calculator

Compute seven non-cryptographic checksums on any text or file in your browser. CRC-32, CRC-16, CRC-8, Adler-32, Fletcher-16, byte sum, and XOR — all in one pass, all in pure JS, nothing uploaded.

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When to use which

CRC-32 (IEEE 802.3)
The default integrity check for files, archives, and network transfers. The same polynomial used by zlib, PNG, gzip, and Ethernet frames.
CRC-16-CCITT (XMODEM)
Used in serial protocols, EEPROMs, and legacy storage. Half the width of CRC-32, half the detection strength.
CRC-8
Single-byte CRC for short frames: Bluetooth, SMBus, many 1-Wire devices. Cheap to compute, fine for <16 byte payloads.
Adler-32
Faster than CRC-32, weaker error detection. Used in zlib stream metadata (RFC 1950). Don't use for tamper detection.
Fletcher-16
Two parallel 8-bit sums (mod 255). Stronger than a simple sum, weaker than CRC-16. Used in PPP and RFC 1146.
Byte sum (1's complement)
The header checksum in IPv4, TCP, and UDP. Catches a single bit flip, misses even-count flips. The simplest possible integrity check.
XOR-8
XOR of every byte. Catches single-byte errors, misses even-count flips. Common in EEPROM layouts and serial EEPROM defaults.