Gastroesophageal reflux disease (GERD) is a multifaceted disorder that can manifest with both typical symptoms, such as heartburn, and atypical symptoms. Furthermore, symptoms commonly associated with GERD may overlap with conditions related to gut-brain interactions, such as functional heartburn and reflux hypersensitivity. Accurate diagnosis through reflux monitoring is crucial before starting irreversible anti-reflux treatments or prolonged proton pump inhibitor therapy (PPI), especially in cases with excessive belching, suspected rumination, or atypical symptoms. Esophageal pH monitoring, utilizing either catheter-based systems (single or dual sensor) or wireless capsules (e.g., alpHaONE from Laborie or Bravo™ from Medtronic), measures esophageal pH over 24 to 96 hours to identify reflux episodes by detecting pH drops below 4.0. Furthermore, pH-impedance monitoring evaluates resistance to electrical conductivity of esophageal content, distinguishing between acidic, weakly acidic, and weakly alkaline reflux, enhancing the precision of symptom association. This method provides detailed information on reflux characteristics, including its extent, velocity, clearance time, and bolus direction. It also utilizes useful diagnostic parameters such as the post-reflux swallow-induced peristaltic wave index and mean nocturnal baseline impedance that may aid in phenotyping patients with refractory GERD.