The typical wet lab user often annotates smaller sequences in the GenBank format, but resulting files are not accepted for database submission by NCBI. This makes submission of such annotations a cumbersome task. Here we present “GB2sequin” an easy-to-use web application that converts custom annotations in the GenBank format into the NCBI direct submission format Sequin. Additionally, the program generates a “five-column, tab-delimited feature table” and a FASTA file. Those are required for submission through BankIt or the update of an existing GenBank entry. We specifically developed “GB2sequin” for the regular wet lab researcher with strong focus on user-friendliness and flexibility. The application is equipped with an intuitive graphical interface and a comprehensive documentation. It can be employed to prepare any GenBank file for database submission and is freely available online at https://chlorobox.mpimp-golm.mpg.de/GenBank2Sequin.html.