Luhn Checksum Validator

Validate numbers that use the Luhn algorithm (IMEI, many account/card-like IDs). Client-side only.

Input (digits; spaces/dashes ignored)

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Normalized digits

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Valid?

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Luhn check digit (for prefix w/out last digit)

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Fix suggestion

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Step	Detail

Note: Luhn alone does not prove authenticity; it only catches common typos.