🔒 Processed locally — never uploaded to any server
What this checks
- Length: must be exactly 18 characters
- Region code: first 6 digits must match a known administrative division (GB/T 2260)
- Birth date: digits 7-14 must be a valid YYYYMMDD date
- Checksum: last digit verified by ISO 7064:1983 MOD 11-2 (GB 11643 standard)
ID number structure
- Digits 1-2: province / municipality code
- Digits 3-4: prefecture code
- Digits 5-6: county / district code
- Digits 7-14: birth date (YYYYMMDD)
- Digits 15-17: sequence (odd=male, even=female)
- Digit 18: checksum (0-9 or X)