Xylan is the second most abundant and renewable biopolymer component of plant cell walls, has attracted a lot of attention in a variety of industrial uses. Chemical alteration known as carboxymethylation has been identified as a key strategy for improving xylan's functional characteristics and expanding its range of applications. This review explores the principles, techniques, and applications of xylan carboxymethylation. First, the basic ideas behind the structure and characteristics of xylan are explained. Next, carboxymethylation techniques are thoroughly examined, along with reaction mechanisms and important variables. This review highlights the importance of carboxymethylation as a tactical method for customizing xylan for a variety of industrial uses, opening the door for more developments and breakthroughs in this field.