This article introduces a series of papers on new guidance for the GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach. Core GRADE was produced in response to the need for a concise, well organised exposition of the key elements of GRADE that users require to make optimal judgments about certainty of evidence and strength of recommendations. This series is primarily aimed at systematic review authors, guideline developers, and health technology assessment practitioners, along with evidence based medicine educators who help clinicians to understand and use GRADE to guide clinical care. In producing Core GRADE, the authors address the problems of out-of-date and poorly organised guidance resulting from publication of the many GRADE papers over 20 years.