Ubiquitin-like modifier involved in formation of autophagosomal vacuoles (autophagosomes). Plays a role in mitophagy which contributes to regulate mitochondrial quantity and quality by eliminating the mitochondria to a basal level to fulfill cellular energy requirements and preventing excess ROS production. In response to cellular stress and upon mitochondria fission, binds C-18 ceramides and anchors autophagolysosomes to outer mitochondrial membranes to eliminate damaged mitochondria. While LC3s are involved in elongation of the phagophore membrane, the GABARAP/GATE-16 subfamily is essential for a later stage in autophagosome maturation. 3 different light chains, LC1, LC2 and LC3, can associate with MAP1A and MAP1B proteins. The precursor molecule is cleaved by ATG4 (ATG4A, ATG4B, ATG4C or ATG4D) to expose the glycine at the C-terminus and form the cytosolic form, LC3-I (PubMed:30661429). The processed form is then activated by APG7L/ATG7, transferred to ATG3 and conjugated to phosphatidylethanolamine (PE) phospholipid to form the membrane-bound form, LC3-II (By similarity). During non-canonical autophagy, the processed form is conjugated to phosphatidylserine (PS) phospholipid (By similarity). ATG4 proteins also mediate the delipidation of PE-conjugated forms (By similarity). In addition, ATG4B and ATG4D mediate delipidation of ATG8 proteins conjugated to PS during non-canonical autophagy (By similarity). Belongs to the ATG8 family.