The aim of this ESC Guideline is to help health professionals manage people with heart failure (HF) according to the best available evidence. Fortunately, we now have a wealth of clinical trials to help us select the best management to improve the outcomes for people with HF; for many, it is now both preventable and treatable. This guideline provides practical, evidence-based recommendations. We have revised the format of the previous 2016 ESC HF Guidelines 1 to make each phenotype of HF stand-alone in terms of its diagnosis and management. The therapy recommendations mention the treatment effect supported by the class and level of evidence and are presented in tables. For HF with reduced ejection fraction (HFrEF), the tabular recommendations focus on mortality and morbidity outcomes. Where there are symptomatic benefits, these are highlighted in the text and/or in the web appendices. Detailed summaries of the trials underpinning the recommendations are available in the web appendices. For diagnostic indications, we have suggested investigations that all patients with HF should receive, and investigations that can be targeted to specific circumstances. As diagnostic tests have rarely been subject to randomized controlled trials (RCTs), most of the evidence would be regarded as level C. However, that does not mean that there has not been appropriate rigorous evaluation of diagnostic tests. In this guideline, we have decided to focus on the diagnosis and treatment of HF, not on its prevention. Management of CV risk and many CV diseases [especially systemic hypertension, diabetes mellitus, coronary artery disease, myocardial infarction (MI), atrial fibrillation (AF), and asymptomatic left ventricular (LV) systolic dysfunction] will reduce the risk of developing HF, which is addressed by many other ESC Guidelines and in s ection 9.1 of the current guideline. 2 � 7 This guideline is the result of a collaboration between the Task Force (including two patient representatives), the reviewers, and the ESC CPG Committee. As such, it is a consensus/majority opinion of the experts consulted in its development.