This DNAqua-Net topical issue edited by the leaders of Working Group 1 (DNA barcode references), Torbjørn Ekrem (Norway), Fedor Ciampor (Slovakia) and DNAqua-Net manager Alexander Weigand (Luxembourg) welcomes submissions on DNA and environmental DNA metabarcoding and metagenomics with a focus on the underlying reference databases. Undoubtly, DNA barcode reference libraries are of immense importance for correct identification of organisms using DNA barcoding and metabarcoding. We welcome contributions that focus on opportunities and challenges related to construction of reference databases and analysis of reference data. Furthermore, we welcome publications that provide and describe reference data for any organismal group.