Current diagnostic testing for gastroesophageal reflux disease (GERD) include endoscopy, ambulatory pH and intraluminal impedance monitoring. However, they are suboptimal and do not measure chronicity of reflux. Recently, a mucosal impedance (MI) device has been developed to measure esophageal epithelial conductivity changes, a marker of chronic GERD. The aim of this review is to summarize the use of MI testing (MIT) for the evaluation and management of esophageal disease. MIT is a minimally invasive and simple through-the-scope procedure performed during endoscopy. It allows for a rapid derivation of MI values within seconds without an uncomfortable overnight pH- impedance catheter. The MI values can correlate with histological findings of epithelial barrier dysfunction, normalize with effective treatment, and show promise for differentiating GERD from non-GERD conditions such as eosinophilic esophagitis (EoE). In conclusion, endoscopic MIT measurement can differentiate esophageal disorders instantly during endoscopy. It may not only serve as an important tool in diagnosing of GERD but also help guide therapy in clinically difficult situations as a surrogate to predict the treatment response.