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The Chicago classification is the classification of esophageal motility disorders with high-resolution manometry. Version 4.0, published in 2021, recommends using a standardized protocol with swallows in both supine and sitting positions, as well as challenge tests (multiple rapid swallows, rapid drink challenge, solid swallows). Motility disorders are categorized into two groups: esophagogastric junction (EGJ) relaxation disorders and peristaltic disorders. Compared to the previous version, the main changes concern type III achalasia, EGJ outflow obstruction, and ineffective esophageal motility. To diagnose type III achalasia, 100% of absent or premature contractions (with at least 20% of premature contractions) are required alongside an elevated integrated relaxation pressure (IRP). The diagnosis of EGJ outflow obstruction requires an elevated IRP in both supine and sitting positions and should be confirmed with a timed barium swallow or measurement of EGJ distensibility with impedance planimetry. Ineffective esophageal motility is defined by more than 70% of ineffective contractions or at least 50% of absent contractions in a context of normal EGJ relaxation.