[Isoform 1]: Catalyzes the transfer of L-fucose, from a guanosine diphosphate-beta-L-fucose, to the N-acetyl glucosamine (GlcNAc) of a distal alpha2,3 sialylated lactosamine unit of a glycoprotein- or a glycolipid-linked sialopolylactosamines chain or of a distal or internal lactosamine unit of a neutral glycoprotein- or a glycolipid-linked polylactosamines chain through an alpha-1,3 glycosidic linkage and participates in surface expression of the sialyl Lewis X (sLe(x)), Lewis X (Le(x)) and non sialylated VIM2 determinants (PubMed:10728707, PubMed:1339443, PubMed:1520296, PubMed:17604274, PubMed:29593094, PubMed:7650030, PubMed:9363434, PubMed:9451035). Moreover transfers fucose to H-type 2 (Fucalpha1-2Galbeta1-4GlcNAc) chain acceptor substrates and participates in difucosylated sialyl Lewis x determinants (PubMed:1339443, PubMed:17604274). Also fucosylates a polylactosamine substrate having a 6 sulfate modification at the GlcNAc moiety and gives rise to sialyl and non-sialyl 6-sulfo lewis X (PubMed:10728707). Does not have activity towards type 1 ((Galbeta1-3GlcNAc)) and H-type 1 chain (Fucalpha1-2Galbeta1-3GlcNAc) acceptors substrates (PubMed:1339443, PubMed:17604274, PubMed:9363434). {ECO:0000269|PubMed:10728707, ECO:0000269|PubMed:1339443, ECO:0000269|PubMed:1520296, ECO:0000269|PubMed:17604274, ECO:0000269|PubMed:7650030, ECO:0000269|PubMed:9363434, ECO:0000269|PubMed:9451035}. [Isoform 2]: Does not have alpha(1,3)-fucosyltransferase activity. . This is the function of Ensembl gene identifier ENSG00000156413 (FUT6, fucosyltransferase 6).