What is CRC?
CRC (Cyclic Redundancy Check) is a fast, non-cryptographic checksum used to detect accidental changes to data. It treats the input as a large binary number and computes the remainder of a polynomial division, producing a short check value such as CRC32. CRCs are used in network protocols, ZIP and PNG files, Ethernet and storage devices to catch transmission or storage errors. CRC is for error detection only — it is not secure against deliberate tampering.
How CRC works
CRC is a one-way cryptographic hash. At a high level it works like this:
- Your input is padded and broken into fixed-size blocks.
- Each block is mixed into an internal state through many rounds of bitwise operations.
- After the final block, the internal state is output as a fixed-length digest.
Every input bit affects the whole result, so a single character change produces a completely different digest — and the digest cannot be reversed back into the input.
How to use
- Type or paste your text into the input box.
- The CRC hash is calculated automatically as you type.
- Choose your output encoding (Hex or Base64) if needed.
- Click Copy to copy the digest to your clipboard.
Common uses
- Verifying file and data integrity with checksums.
- Fingerprinting and deduplicating content.
- Detecting accidental corruption or changes.
- Indexing or comparing data without storing the original.
Frequently asked questions
Is CRC a secure hash?
No. CRC detects accidental errors but is not cryptographically secure.
What is CRC32?
A common 32-bit CRC variant used in ZIP, PNG and Ethernet.
When should I use CRC instead of a hash?
Use CRC for fast error detection; use SHA-256 when security matters.