The CDC and AAP have worked together to revise the developmental milestones included in the Learn the Signs. Act Early. program, which helps parents identify autism and developmental delays in their children. (Learn about the revision.)
You can use the online checklists or print PDF checklists or there is also a free CDC Milestone Tracker app. The new evidence-based milestones are written so that 75% of children in an age group should have reached that milestone. If you are concerned after doing a milestones checklist, check out: https://www.cdc.gov/ncbddd/actearly/concerned.html.
Learn more about development: https://gooddayswithkids.com/2022/02/08/resources-development/ and developmental screenings: https://gooddayswithkids.com/2019/02/13/asq-screening/