This tool computes an 8-bit CRC checksum of any text or raw hex bytes and shows it in both hexadecimal and decimal, updating live. CRC-8 is widely used in low-level protocols — SMBus, 1-Wire sensors, and many embedded packets — to detect accidental corruption of short messages.
How it works
CRC-8 treats the input as a polynomial over GF(2) and computes the remainder when divided by the generator polynomial 0x07 (x^8 + x^2 + x + 1). This implementation precomputes a 256-entry lookup table from the polynomial, then processes the data one byte at a time: starting from the initial value 0x00, each input byte is XORed into the running CRC and the result indexes the table. Because this variant uses no bit reflection and no final XOR, the table is built in the straightforward most-significant-bit-first direction.
Example and notes
The canonical CRC check string 123456789 produces 0xF4 with this CRC-8/SMBUS variant, so you can use it to confirm the calculator is correct. Note that other CRC-8 variants (such as CRC-8/MAXIM or CRC-8/DARC) use different polynomials, reflection, or initial values and will give different results.
CRC-8 detects accidental errors only — it is not cryptographic and is easy to forge. Use it for quick integrity checks on short data, never for security. Everything is computed in pure JavaScript in your browser; nothing is uploaded.