Laravel Migration Error : Syntax error or access violation: 1071 Specified key was too long; max key length is 767 bytes laravel 5.3

[Illuminate\Database\QueryException] SQLSTATE[42000]: Syntax error or access violation: 1071 Specified key was too long; max key length is 767 bytes (SQL: alter tabl e users add unique users_email_unique(email))

[PDOException] SQLSTATE[42000]: Syntax error or access violation: 1071 Specified key was too long; max key length is 767 bytes

whats wrong? im using laravel 5.3

via muzamil indra