After performing gapfilling on a metabolic model, you can sort the “Reactions” tab of the output table by the “Gapfilling” column to see which reactions were added. In order to compare the differences between the draft model and the gapfilled model, look at the directionality of the reaction in the “Equation” column of the “Reactions” tab of the output table. If the directionality is reversible in the gapfilled model, i.e. “<=>”, this means that the reaction was already in the draft model, albeit previously irreversible, and gap-filling made it reversible. However, if the reaction is irreversible e.g., “=>” or “<=”, then this means it is a new reaction that wasn’t previously present in the draft model, and has been added to the model by the gapfilling algorithm.