Extracranial-intracranial (EC-IC) bypass is a crucial technique in modern neurosurgery. It can be utilized for blood flow augmentation in cases of chronic cerebral ischemia, as well as for blood flow replacement when a major cerebral artery needs to be sacrificed. This represents a classification based on the procedural purpose. EC-IC bypass can also be categorized into high-, medium-, and low-flow procedures depending on the amount of blood flow delivered to the brain. By combining different procedures and incorporating advanced techniques—such as balloon occlusion tests, indocyanine green (ICG) videography, electrophysiological monitoring, and real-time pressure measurement—it is possible to optimize surgical efficacy while minimizing trauma and risks. This allows for an individualized bypass procedure tailored to the specific needs of each patient.