Friction stir welding (FSW) is the latest method in metal joining processes which has more significant potential when welding metal alloys. Its extensive use is for aluminium alloys and their utility has now extended to various materials including magnesium, copper, steel and thermoplastics. The technique of welding alloys has been implied in major industries such as aerospace, railway, shipbuilding land transportation. This review article focuses on basics of FSW, FSW input parameters, design Considerations of FSW tool, and friction stir welded alloy materials. The present state of this welding technique is studied to suggest the required input parameters by mainly focusing on the rotational speed of tool, weld speed and other input parameters associated with welding, and thereby understanding the defect formation and characteristics of the welded materials. © 2019 Elsevier Ltd. All rights reserved.