Checksum Calculators
CRC-32 Checksum Calculator
Calculate CRC-32/ISO-HDLC for UTF-8 text. Its eight-character hexadecimal value is useful for checking accidental changes.
✓ Every tool runs in your browser. We do not upload your input or output.
Keyboard shortcuts
Ctrl/⌘ + Enter: process
Ctrl/⌘ + Shift + F: full screen
Esc: exit full screen
Ctrl/⌘ + F in editor: search
How to use
- Enter the exact text whose bytes you want to check.
- Run the tool and inspect the eight-digit hex result.
- Compare it with a reference using CRC-32/ISO-HDLC or the same common ZIP/Ethernet parameters.
- Check line endings and encoding when results differ.
Examples
Verify a common CRC check value
This standard text sequence verifies the chosen CRC-32 parameters.
123456789
0xcbf43926
Detect accidental byte changes
CRC-32/ISO-HDLC is a widely used checksum variant. The calculator starts with the standard initial state, processes UTF-8 bytes in reflected form, and applies the final XOR. Its result is shown as eight lowercase hexadecimal characters. Enter 123456789 to see the familiar check value 0xcbf43926. That value is a useful diagnostic if another tool reports a different CRC for the same apparent text.
A CRC mismatch can indicate a changed payload, newline, or encoding. It can also mean the other system uses a different CRC-32 variant. Record the full name and parameters when documenting an integration. This page treats the editor content as text; it does not calculate over raw bytes of a binary file. The computation runs in your browser and the input is not uploaded.
CRC-32 is not a cryptographic hash. Someone able to alter a message can also calculate a new CRC for it. Use SHA-256 to compare against a trusted checksum, and use HMAC or a signature when you need authentication. The related CRC-16 calculator covers a separate 16-bit protocol variant.
Frequently asked questions
Which CRC-32 variant is this?
CRC-32/ISO-HDLC, with polynomial 0x04c11db7 in normal form, reflected processing, initial 0xffffffff, and final XOR 0xffffffff.
Is CRC-32 secure against tampering?
No. It is designed to detect accidental errors, not authenticate a sender.
Does it hash a binary upload as raw bytes?
No. Uploaded files are read as text, then encoded as UTF-8.
Why is the output eight hex characters?
CRC-32 produces 32 bits, which require eight hexadecimal digits.