Which CRC-8 variant does this tool compute?

CRC-8/SMBUS: polynomial 0x07, initial value 0x00, no input or output reflection, no final XOR. There are dozens of named CRC-8 parameter sets in circulation (CRC-8/BLUETOOTH, CRC-8/MAXIM, CRC-8/AUTOSAR, and more), each with a different polynomial and/or reflection setting, so a CRC-8 checksum from one system won't necessarily match another's even for identical input; SMBUS is one of the most common defaults.

Why is CRC-8 output only 2 hex characters?

CRC-8 always produces an 8-bit result regardless of input size, and 8 bits written as hex is exactly 2 characters (each hex digit encodes 4 bits, so 8 / 4 = 2). That's the smallest checksum in this category; it trades collision resistance for extremely cheap computation, which is the point in resource-constrained embedded contexts.

What is CRC-8 actually used for?

Small embedded and communication protocols where every byte of overhead matters: SMBus and I2C packet error checking, some automotive CAN bus payloads, 1-Wire device protocols (Maxim/Dallas sensors), and various low-level firmware checksums. It's not meant for general file integrity, where CRC-32 or a cryptographic hash is standard.

Does this tool send my text to a server?

No. The CRC-8 checksum is computed entirely in your browser using a hand-written, table-driven TypeScript implementation, so nothing you type here is transmitted anywhere.

CRC8 Calculator - Compute CRC-8/SMBUS Checksum Online

Overview

Introduction

CRC-8 is the smallest checksum in this category, an 8-bit result meant for contexts where every byte of protocol overhead counts, like embedded SMBus or 1-Wire device communication.

This tool computes the CRC-8/SMBUS variant (polynomial 0x07, no reflection) of any text you provide, entirely client-side, useful for verifying an embedded protocol's checksum by hand or matching known test vectors.

What Is CRC8 Calculator?

CRC-8 is an 8-bit cyclic redundancy check: a small polynomial-division-based checksum designed to catch accidental bit errors in short messages, shown here as 2 hexadecimal characters.

This tool specifically implements CRC-8/SMBUS: polynomial 0x07 in its normal (non-reflected) form, initial value 0x00, and no output reflection or final XOR, matching the reveng CRC catalogue's parameters for that name.

How CRC8 Calculator Works

Your UTF-8 encoded text is processed one byte at a time through a lookup table built from the 0x07 polynomial, treating the checksum's most significant bit first (unlike CRC-16 and CRC-32 elsewhere in this category, which process least-significant-bit first).

Each byte updates an 8-bit running remainder via table lookup and XOR; the final remainder, with no reflection or XOR applied, is hex-encoded into the 2-character output.

When To Use CRC8 Calculator

Use CRC-8 when implementing or debugging a protocol that specifically calls for it, like SMBus packet error checking, 1-Wire device communication, or an automotive/embedded checksum field.

Don't use CRC-8 for general file integrity or anything where collision resistance matters; its 8-bit space is far too small to resist deliberate tampering, and CRC-32 or a cryptographic hash is the right tool for that.

Often used alongside CRC16 Calculator, CRC32 Calculator and CRC24 Calculator.

Features

Advantages

Extremely cheap to compute, ideal for resource-constrained microcontrollers.
Minimal protocol overhead: just one byte of checksum per message.
Well suited to catching accidental single- and multi-bit errors in short embedded messages.

Limitations

Only 256 possible checksum values, so it cannot meaningfully resist deliberate forgery or distinguish large inputs reliably.
Many incompatible CRC-8 parameter sets exist; matching a specific system's checksum requires confirming its exact polynomial and reflection settings.
Not a substitute for a cryptographic hash when integrity against an adversary matters.

Examples

Hashing the standard CRC check string

Input

123456789

Output

f4

The official CRC-8/SMBUS check value for the ASCII string "123456789", the standard sanity-check input used across the reveng CRC catalogue.

Hashing a short greeting

Input

Hello, world!

Output

bc

13 bytes of UTF-8 text reduced to the 2-character CRC-8/SMBUS checksum.

Best Practices & Notes

Best Practices

Confirm which CRC-8 variant (polynomial and reflection) a target system actually uses before assuming this SMBUS-parameter tool will match it.
Use CRC-8 only for accidental-error detection in short, low-stakes embedded messages, never for security.
Reach for CRC-16 or CRC-32 instead when a larger checksum space is needed for longer data.

Developer Notes

Implemented as a table-driven, non-reflected (MSB-first) CRC using polynomial 0x07, distinct from this category's CRC-16/CRC-32 tables which are both reflected/LSB-first. Verified against the official CRC-8/SMBUS check value (0xf4 for the ASCII string "123456789", the standard reveng CRC catalogue sanity check) plus an independently confirmed vector for "Hello, world!".

CRC8 Calculator Use Cases

Verifying an SMBus or 1-Wire device's packet checksum by hand
Reproducing an embedded protocol's CRC-8 field while debugging firmware
Confirming a CRC-8 implementation matches the standard SMBUS check value
Teaching CRC fundamentals with the smallest, easiest-to-trace example in this category

Common Mistakes

Assuming all "CRC-8" checksums use the same polynomial; dozens of incompatible named variants exist.
Using CRC-8 where a cryptographic hash is actually needed, it offers no resistance to deliberate tampering.
Forgetting this tool is non-reflected while this category's CRC-16/CRC-32 tools are reflected, so bit ordering intuition from those doesn't transfer.

Tips

If your target system's CRC-8 doesn't match this tool's output, it's very likely using a different polynomial or reflection setting; check the reveng catalogue's other CRC-8 entries.
For a Usenet/scene-style file checksum instead, this category's CRC-32-based SFV tools are the closer match.

CRC8 Calculator