I am Going to tell you about the Byjus app which had a collection of very low quality video is terms of information. First of all when I tried the Byjus app in my 8th class, then I was very excited because its UI and Way Of teaching is very good in videos like in Physics and chemistry with ANIMATIONS, But when I gave the exam after studying with this app, the result was very poor.
Reason: It Only Teaches In NCERT Syllabus But it is not good for CBSE Board Exams.