Category guide
Checksum Calculators
Checksums help detect accidental changes to a message when both sides use the same algorithm and byte sequence. Choose the exact CRC variant named by the protocol, then compare a known test value before checking live data. All calculations on this site run locally.
Choose the right tool
CRC-16 Checksum Calculator
Calculate CRC-16/CCITT-FALSE when a device or file format specifies that variant.
CRC-32 Checksum Calculator
Calculate CRC-32/ISO-HDLC for a format that expects the common 32-bit value.
SHA-256 Hash Generator
Use a SHA-256 digest when a specification calls for a cryptographic fingerprint instead of CRC.
HMAC Generator
Use a keyed HMAC when the goal is to verify who produced a message with a shared secret.
All tools
Example workflow: check a protocol test frame
- Read the protocol specification for the full CRC variant, not only the width of the result.
- Enter a published test message in the matching calculator and compare the hexadecimal checksum.
- Use the exact bytes and line endings of your frame when checking a real message.
Before you use the result
CRC-16 and CRC-32 detect accidental changes but are not authentication or tamper protection. Different CRC variants can have the same output width but different parameters. The tools operate on UTF-8 text input, so byte encoding matters.
The variant name matters
Two 16-bit CRC algorithms can return different values for the same text. CRC-16/CCITT-FALSE Calculator and CRC-32/ISO-HDLC Calculator implement specific variants, so compare the complete variant name in the protocol documentation. A standard test vector such as 123456789 helps catch a mismatch before you investigate a large frame.
Choose a stronger check when needed
A CRC detects transmission or storage errors, but someone can modify a message and recompute it. If a specification requires a cryptographic digest, use SHA-256 Hash Generator. If the recipient must verify a shared secret, use HMAC Generator and follow the protocol’s key and message encoding rules. Neither checksum calculator substitutes for authentication.