National Testing Agency has released syllabus for JEE Main 2020. Detailed syllabus for JEE Main 2021 is yet to be released by NTA. But it is expected that there won't be any major changes in JEE Main 2021 syllabus. Here is the link for official JEE Main syllabus released by NTA .

https://jeemain.nta.nic.in/WebInfo/Handler/FileHandler.ashx?i=File&ii=13&iii=Y

For syllabus along with chapter wise marks distribution visit this link :

https://engineering.careers360.com/articles/jee-main-syllabus-weightage

Hey

You can find the detailed syllabus of JEE MAINS by going through the following link;

https://www.google.com/amp/s/engineering.careers360.com/articles/jee-main-syllabus/amp

And to know the weightage of each chapter and the pattern of question paper , you can follow the given link:

https://www.google.com/amp/s/engineering.careers360.com/articles/jee-main-syllabus-weightage/amp

Hope it helps!