Luhn checker — card/IMEI checksum (local)
Paste a number (spaces or hyphens OK) to verify the Luhn mod-10 checksum, see the expected check digit, walk the doubling steps, or bulk-check a list — all in your browser with nothing stored.
Frequently asked questions
No. Luhn checksums are computed entirely in your browser; digit strings are not uploaded or stored. Nothing is sent to LocalTools servers for processing.
No. Luhn only catches some digit typos. It does not prove issuer, funding, or authorization. Use synthetic test numbers for learning; avoid pasting live payment account numbers when you can.