CRC Calculator
Compute CRC-8, CRC-16, CRC-32, CRC-32C, CRC-64 and Adler-32 checksums from text or files. Hex and decimal output, 15 algorithms, large files hashed in a background worker — all local in your browser.
What is a CRC?
CRC stands for Cyclic Redundancy Check — a checksum computed by polynomial division over the data bytes. It detects accidental corruption: if a single bit flips during transfer or storage, the CRC of the received data will (almost always) differ from the transmitted one, which is why protocols like Modbus, HDLC, USB, Ethernet and ZIP all rely on it.
How is CRC different from a cryptographic hash like SHA-256?
CRC is an error-detecting code, not a security primitive. It is fast and catches random corruption, but it is trivially reversible — anyone can craft data with a chosen CRC — so it must never be used to verify authenticity, sign anything or store passwords. SHA-256 and friends are one-way, collision-resistant functions designed exactly for those purposes.
Which algorithms are included?
Fifteen: CRC-8/SMBUS, CRC-8/1-WIRE (Maxim), CRC-8/DVB-S2, CRC-16/IBM (ARC), CRC-16/CCITT-FALSE, CRC-16/KERMIT, CRC-16/XMODEM, CRC-16/MODBUS, CRC-24 (OpenPGP), CRC-32, CRC-32/MPEG-2, CRC-32/JAMCRC, CRC-32C (Castagnoli), Adler-32 and CRC-64/GO-ECMA. They cover the variants most commonly asked for in embedded, networking and file-format work.
Why do CRC-16/CCITT-FALSE, KERMIT and XMODEM give different results for the same data?
They share the same polynomial (0x1021) but differ in the initial value, bit reflection and final XOR. "Same CRC-16" is therefore ambiguous — always check which exact variant your protocol or device specifies, then pick it from the list here.
Does UTF-8 vs Latin-1 matter?
Yes. CRC operates on bytes, and the encoding decides which bytes your text becomes. Pure ASCII input is identical in both, but characters like é or 中 differ: UTF-8 uses two or three bytes per character, Latin-1 only one (and cannot represent 中 at all). Choose the encoding your receiving system expects.
How are large files handled?
The File tab streams the file into a Web Worker and computes the checksum chunk by chunk off the main thread, showing a progress bar. The window stays responsive and multi-megabyte files finish in a moment; the file never leaves your device.
Why both hex and decimal output?
Hex is the convention in documentation, datasheets and debuggers (CRC-32 of "123456789" is CBF43926), while some serial protocols, PLC tools and log formats expect the plain decimal value. The UPPERCASE toggle matches whichever notation your reference uses, and each field copies with one click.
Can CRC correct errors, not just detect them?
Only in special constructions (error-correcting codes like Reed–Solomon build on similar math). A plain CRC tells you the data is damaged but not where or how to repair it. For repair you need redundancy schemes such as FEC or parity files.
Is anything uploaded to a server?
No. Text and files are checksummed locally in your browser using JavaScript; there are no network requests at all. It is safe to checksum private files — though remember a CRC is not a security tool.
Which CRC should I use for my project?
Whatever the other side already expects — CRC is only useful if sender and receiver compute the same variant. For new designs CRC-32 or CRC-32C are good defaults (strong detection, hardware support on modern CPUs); for Modbus devices use CRC-16/MODBUS, and for HDLC/PPP use CRC-16/CCITT-FALSE or KERMIT as specified.
How to Use CRC Calculator
This CRC calculator computes checksums for text or files using 15 common algorithms: CRC-8/SMBUS, CRC-8/1-WIRE, CRC-8/DVB-S2, CRC-16/IBM (ARC), CRC-16/CCITT-FALSE, CRC-16/KERMIT, CRC-16/XMODEM, CRC-16/MODBUS, CRC-24 (OpenPGP), CRC-32, CRC-32/MPEG-2, CRC-32/JAMCRC, CRC-32C, Adler-32 and CRC-64/GO-ECMA. Results appear in both hex and decimal, with an uppercase toggle and one-click copy. Files are hashed in a background Web Worker with a progress bar, and everything runs locally in your browser.
- On the Text tab, type or paste your input; the checksum updates as you type.
- Pick the character encoding: UTF-8 for modern text, Latin-1 (ISO-8859-1) when the receiving device expects one byte per character.
- Select the algorithm your protocol or datasheet specifies — CRC-32 is preselected. The same data gives different values per algorithm.
- Read the HEX and Decimal fields, flip the UPPERCASE switch to match your reference notation, and use Copy to grab either value.
- For files, switch to the File tab and click the drop zone (or drag a file in): the hashing runs in a worker with a live progress bar and the file stays on your device.
Sanity check: the CRC-32 of the ASCII string "123456789" is CBF43926 (decimal 3421780262). If a device disagrees with your result, you are almost certainly using a different CRC variant — check its exact polynomial, init value and reflection settings before blaming the bytes.
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