What is a CRC checksum?

A CRC (Cyclic Redundancy Check) checksum is a value computed from data using polynomial division. It detects accidental changes to raw data in digital networks and storage. The sender computes a CRC before transmission; the receiver recomputes it and compares. A mismatch indicates data corruption. CRC is not a cryptographic hash and should not be used for security.

What is the difference between CRC-8, CRC-16, and CRC-32?

CRC-8 produces an 8-bit (1-byte) checksum with 256 possible values, suitable for small data packets. CRC-16 produces a 16-bit (2-byte) checksum with 65,536 values, used in Modbus and USB. CRC-32 produces a 32-bit (4-byte) checksum with over 4 billion values, used in Ethernet, ZIP, PNG, and gzip. Longer CRCs detect more error patterns.

What is the CRC-32 of "123456789"?

The CRC-32 (IEEE 802.3) of the ASCII string "123456789" is 0xCBF43926 (decimal 3421780262). This is the standard test vector used to verify CRC-32 implementations. If your implementation returns a different value, it likely uses a different polynomial or initial value.

How is CRC different from MD5 or SHA hashing?

CRC is designed for fast error detection, not security. It uses simple polynomial arithmetic and is extremely fast, often implemented in hardware. MD5 and SHA are cryptographic hash functions designed to be one-way and collision-resistant. CRC can be easily reversed or forged, so it should never be used for password hashing, digital signatures, or data integrity verification against malicious tampering.

CRC-32 is used in Ethernet frame check sequences, ZIP and gzip file formats, PNG image integrity, and SATA storage. CRC-16 is used in Modbus industrial protocol, USB data packets, Bluetooth, and HDLC framing. CRC-8 is used in ATM cell headers, 1-Wire bus communication, and embedded sensor networks. Nearly every digital communication protocol includes some form of CRC.

Can CRC detect all errors?

No. CRC can detect all single-bit errors, all double-bit errors (for suitable polynomials), all odd numbers of bit errors, and all burst errors shorter than the CRC width. However, CRC cannot detect all possible multi-bit errors. CRC-32 has a 1 in 4,294,967,296 chance of missing a random error. For critical applications, combine CRC with other error-detection or error-correction codes.

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CRC Checksum Calculator

A CRC (Cyclic Redundancy Check) is a checksum computed by polynomial division over binary data. CRC-32 uses the IEEE 802.3 polynomial and produces a 32-bit value (8 hex digits). The standard test vector "123456789" yields CRC-32 = 0xCBF43926. CRC detects accidental errors in Ethernet, ZIP, PNG, and gzip but is not cryptographically secure.

Calculate CRC-8, CRC-16, and CRC-32 checksums online. Enter text or hex input and get instant CRC values in hexadecimal and decimal. Free CRC checksum calculator with lookup-table performance, presets, and no signup required.

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About CRC Checksums

CRC-8: 8-bit checksum for small data packets, serial communication, and embedded systems.
CRC-16: 16-bit checksum used in Modbus, USB, and Bluetooth protocols.
CRC-32: 32-bit checksum used in Ethernet, ZIP, PNG, and gzip file integrity checks.

CRC vs Cryptographic Hashes

CRC is designed for error detection, not security.
CRC is much faster than MD5 or SHA, ideal for real-time data validation.
For security-sensitive use cases, use SHA-256 or SHA-512 instead.

How to Use

1
Choose input mode
Select Text for plain text input or Hex for raw hexadecimal byte input
2
Enter your data
Type or paste the data you want to compute a CRC checksum for
3
View all CRC values
CRC-8, CRC-16, and CRC-32 results appear instantly in both hexadecimal and decimal
4
Copy the result
Click the copy button next to any hex or decimal value to copy it to your clipboard

Frequently Asked Questions

What is a CRC checksum?: A CRC (Cyclic Redundancy Check) checksum is a value computed from data using polynomial division. It detects accidental changes to raw data in digital networks and storage. The sender computes a CRC before transmission; the receiver recomputes it and compares. A mismatch indicates data corruption. CRC is not a cryptographic hash and should not be used for security.
What is the difference between CRC-8, CRC-16, and CRC-32?: CRC-8 produces an 8-bit (1-byte) checksum with 256 possible values, suitable for small data packets. CRC-16 produces a 16-bit (2-byte) checksum with 65,536 values, used in Modbus and USB. CRC-32 produces a 32-bit (4-byte) checksum with over 4 billion values, used in Ethernet, ZIP, PNG, and gzip. Longer CRCs detect more error patterns.
What is the CRC-32 of "123456789"?: The CRC-32 (IEEE 802.3) of the ASCII string "123456789" is 0xCBF43926 (decimal 3421780262). This is the standard test vector used to verify CRC-32 implementations. If your implementation returns a different value, it likely uses a different polynomial or initial value.
How is CRC different from MD5 or SHA hashing?: CRC is designed for fast error detection, not security. It uses simple polynomial arithmetic and is extremely fast, often implemented in hardware. MD5 and SHA are cryptographic hash functions designed to be one-way and collision-resistant. CRC can be easily reversed or forged, so it should never be used for password hashing, digital signatures, or data integrity verification against malicious tampering.
Where is CRC used?: CRC-32 is used in Ethernet frame check sequences, ZIP and gzip file formats, PNG image integrity, and SATA storage. CRC-16 is used in Modbus industrial protocol, USB data packets, Bluetooth, and HDLC framing. CRC-8 is used in ATM cell headers, 1-Wire bus communication, and embedded sensor networks. Nearly every digital communication protocol includes some form of CRC.
Can CRC detect all errors?: No. CRC can detect all single-bit errors, all double-bit errors (for suitable polynomials), all odd numbers of bit errors, and all burst errors shorter than the CRC width. However, CRC cannot detect all possible multi-bit errors. CRC-32 has a 1 in 4,294,967,296 chance of missing a random error. For critical applications, combine CRC with other error-detection or error-correction codes.