Assessment can be a crucial component in the teaching and learning process and should measure or certify results. Online assessment means using the technology to provide assessment which can be diagnostic, formative or summative and can be considered a valuable tool in higher education as it allows teachers, on one hand, to have quick access to students' performance and, on the other hand, students can receive instant and individual feedback, which helps them to structure their own learning path.There are many different ways to efficiently assess students' learning online, the purpose of this paper is to introduce some online assessment tools and techniques that can be used in education to assess student performance using technology. In general, learning management systems, such as Moodle, use online assessment tools, some of which will be presented, based on the corresponding learning requirements and objectives. Several online assessment techniques, that undeniably support training, engage students, and provide instructors with perception of their students' learning process, will also be analyzed. Furthermore, several tools and techniques related to mathematics will be presented, like for instance STACK (System for Teaching and Assessment using a Computer Algebra Kernel) and iSpring Suite 9. STACK, an online assessment package for mathematics, is an open-source system that supports the development of sophisticated and challenging assessments for STEM subjects, enabling the direct and systematized feedback delivery to help students improve their performance and understanding. The iSpring Suite 9, a fully e-learning toolkit, with a Math equation editor which allows the development of interactive assessments and quizzes for e-Courses. Some advantages and disadvantages about the online assessment process will be also presented.