dev-passwords

Bcrypt password hash authentication fails during database seeding when the stored hash uses a different bcrypt implementation or cost factor than the application's authentication library. Matching the exact library and rounds ensures compatibility and successful login.

To generate a compatible bcrypt hash for Node.js or .NET, identify the specific library used, such as bcryptjs or BCrypt.Net-Next, and apply the same cost factor. Use that library's hash generation function to produce the matching hash for your database.

A bcrypt hash generated in Python may not work with a PHP password_hash system if the bcrypt implementations or cost factors differ. Verifying library compatibility and aligning the rounds ensures the hash is valid across different language stacks.

The best way to diagnose bcrypt library mismatches is to scan project files and seed migrations for library references, verify the configured cost factor, and locate broken or placeholder hashes. Comparing these against the active authentication library resolves login failures.

You should regenerate bcrypt hashes for local test users when integrating a new authentication library, updating the bcrypt cost factor, or replacing placeholder seed migration hashes. This ensures the test database contains valid hashes recognized by the target application.