Hi, I would like to know the format of OBC Certificate for JEE Main? Is there any specific format for 2018?

NO i dont think there is change but still go through it:

JEE Main Reservation Criteria 2018 – The eligibility criteria of JEE Main 2018 constitutes of reservation criteria for certain category candidates. JEE Main 2018 reservation criteria has been prescribed by CBSE, the exam conducting body, on the basis of which admissions will be conducted in the participating institutes. The reservation criteria of JEE Main 2018 is applicable to the following – candidates belonging to SC, ST and OBC categories, female candidates and candidates belonging to Person with Disability (PwD) category. JEE Main reservation criteria 2018 ensures that candidates coming under these categories will have certain advantages in terms of seat allocation, qualifying exam scores, entrance exam scores and age limit over non-reserved category categories. The reservation criteria of JEE Main 2018 also include parameters related to home state and other state quota in terms of admissions offered by the state universities. This means that in JEE Main , a candidate belonging to home state will get preference over other candidate in his or her home state university. It is important to note that candidates coming under JEE Main 2018 reservation criteria will have to produce necessary documents as proof of their reservation. Candidates can check all the details pertaining to reservation criteria of JEE Main 2018 from the article given below.