Khan Academy

Khan Academy is an excellent resource for learning about almost anything. While there isn't a section dedicated to GRE Prep, there is plenty of content that will aid you with your studies, particularly math. Make sure you understand the subjects the GRE examines in order to personalize the Khan Academy GRE to the study resources you want (here are their expert breakdowns of quant concepts on the GRE and the verbal reasoning topics).

To identify the most useful math modules, go to the ETS page, where the test-maker has linked to pertinent portions of the Khan Academy website. Of course, the GRE Verbal is significantly more difficult than the SAT, but the approaches will work just as well. The two exams also cover the same subjects, such as physics, literature, history, and social sciences. However, rather than SAT resources, supplement this learning with GRE practice questions and practice tests! Finally, if you're having trouble finding a certain GRE topic using either of the aforementioned techniques, keep in mind that the Khan Academy website is massive. Simply search for the concept you're struggling with, and you'll almost certainly discover a video that explains it correctly.

Website: https://www.khanacademy.org/