Manual testing, often known as defect testing, is the process of checking software for problems by hand. Without an automation tool or script, testing is considered to be manual testing. Here, the tester simulates an actual user to ensure that every function is fully operational. Manual testing consists of several phases, such as unit testing, integration testing, system testing, and user acceptability testing. The thoroughness of software testing is ensured through the use of test plans, test cases, and test scenarios. Manual testing is done before a software product goes live to find any defects or functionality problems. Manual software testing is a preliminary test that does not require familiarity with any testing tools. Manual testing is crucial due to the fact that "100% automation is not possible," which is a key principle of software testing.