Circuit Board Component Identification: How to Identify PCB Components by Markings, Shape, and Codes

Circuit board component identification means recognizing PCB parts by their reference designators, physical appearance, body markings, polarity marks, package type, and electrical function. The fastest way to identify a component is to start with the PCB silkscreen, match the reference letter to a component type, inspect its shape and package, read any value or top marking, then confirm the result with a datasheet, schematic, BOM, or measurement tool. This guide explains how to identify common PCB components such as resistors, capacitors, inductors, diodes, transistors, MOSFETs, ICs, connectors, fuses, relays, crystals, and test points. It also includes practical examples, common marking codes, polarity clues, mistakes to avoid, and a replacement sourcing checklist.