CRC File Checksum Calculator
Compute CRC-32, CRC-32C, CRC-16, CRC-8 and CRC-64 checksums of a file in your browser and compare with an expected value. No upload, large files supported.
No file selected yet. The checksum appears as soon as you pick a file.
The file is read in chunks inside your browser and is never uploaded.
What is CRC File Checksum?
This tool calculates the CRC checksums of a file — CRC-32 (zip, PNG, Ethernet), CRC-32C (iSCSI, ext4, SCTP), CRC-32/BZIP2, CRC-32/MPEG-2, CRC-16/ARC, CRC-16/MODBUS, CRC-16/CCITT-FALSE, CRC-16/XMODEM, CRC-16/KERMIT, CRC-8/SMBUS, CRC-8/MAXIM and CRC-64/XZ — in a single pass and compares the selected one with an expected value. The file is read in 4 MB chunks locally and is never uploaded.
How to use CRC File Checksum
- Select the CRC variant you want to compare (CRC-32 by default).
- Click the drop zone or drag a file onto it; the file is read in chunks and a progress bar is shown.
- Check the File name and File size shown below to make sure you picked the right file.
- Paste the expected CRC into Expected checksum (hex or decimal) to see Match or Mismatch; all variants are listed in the table below.
Example
A file hash-check.txt containing the 9 bytes "123456789"
cbf43926
CRC-32 of the file; typing 3421780262 (decimal) or CBF43926 into Expected checksum shows Match.
When to use CRC File Checksum
Use it to check the CRC-32 listed for a file in a ZIP archive, SFV file or firmware manifest, or to compute CRCs for embedded update images. CRCs only detect accidental corruption; to verify a download against tampering use a SHA-256 checksum instead.
How CRC File Checksum works
The file is read in 4 MB slices and every slice updates all CRC variants at once, so you get the whole table from a single read. A CRC treats the data as a large binary polynomial and computes the remainder of its division by a fixed generator polynomial (modulo 2). Each variant is defined by width, polynomial, initial value, whether input and output bits are reflected, and a final XOR value (the Rocksoft model). This tool uses a 256-entry lookup table per variant and checks every variant against its catalogue check value — the CRC of the ASCII string 123456789 (for example CRC-32 = cbf43926, CRC-32C = e3069283, CRC-16/MODBUS = 4b37). The result is shown as a big-endian hex number, or in decimal.
Common Use Cases
- Compare a file with the CRC-32 in an SFV (Simple File Verification) list
- Check a firmware image against the CRC in its manifest
- Get the CRC-32 that a ZIP archive should record for a file
- Compute CRC-32C of a blob for cloud storage integrity checks
Security Note
A CRC cannot detect deliberate tampering; anyone can modify a file and keep its CRC. Use SHA-256 or a signature for security-relevant verification.
FAQs
Is the file uploaded?
No. It is read with the browser File API and processed locally in chunks, so even large files work without leaving your device.
Why does my CRC-32 differ from the cksum command?
POSIX cksum uses a different, unreflected CRC-32 and appends the file length. ZIP, gzip, PNG and SFV files use the CRC-32 shown here.
Can I enter the expected CRC in decimal?
Yes. Expected checksum accepts hex (any case, optional 0x) or a decimal number for CRC variants.