How to fix auth/invalid-user-import: User record being imported is malformed in Firebase

First, ensure your user import data follows Firebase's required structure. Each user record should include required fields like UID, and optional fields like email, phoneNumber, etc. must be properly formatted. Key validation points include: UID must be present and max 128 characters with only alphanumeric and certain symbols; email must be valid format if provided; phone must be E.164 format if provided; booleans must be true/false, not strings; timestamps must be ISO 8601 format.

Examine your import data for common formatting problems: Email validation - ensure emails have proper format ([email protected]); Phone number validation - must be E.164 format (+12345678901); Password hash validation - must be Buffer if migrating passwords; UID validation - must be 1-128 characters, only alphanumeric, hyphen, underscore, period.

Firebase Admin SDK provides tools to validate user import data before attempting the actual import. Use auth.importUsers() with dryRun: true to validate without importing. This will return success/failure counts and detailed error messages for each problematic record. You can also validate individual fields programmatically by checking UID length/format, email regex, phone format, and boolean fields.

After identifying problematic records, fix them and retry the import. Create a clean import function with error handling that tracks successful imports and failed users. Implement retry logic with exponential backoff. Common fixes include: trimming whitespace from string fields, ensuring boolean fields are actual booleans, converting UIDs to strings, and fixing format issues.

For large user imports, use batching to avoid timeouts and memory issues. Implement batch import function that processes users in configurable batch sizes (start with 100-500). Add delays between batches to avoid rate limiting. Monitor memory usage during imports and adjust batch size accordingly. Track progress and handle partial failures gracefully.

After successful import, verify the users by fetching user records with auth.getUser(uid). Check a sample of imported users to ensure they were created correctly. Clean up temporary files and data used during the import process. Log import statistics including total time, success rate, and common error types for future reference.