Hello Aspirant ,

Form your profile I can assume that you want free video lectures for JEE Mains / advanced or other engineering entrance exam (most of them have common syllabus)

There are many YouTube channels providing free videos but only some of them are worth watching and are mostly useful for JEE Mains  , I have listed some good channels :

• Physicswallah( full course )
• Vedantu( full course )
• Unacademy ( full course )
• Organic Chemistry ( for particular topics only)
• Physics galaxy  etc

Please do not focus only on these videos as most do not go in depth and just try to sell their paid coaching , books +coaching(optional) will be the best idea.

Hope this helps.