Updated publication reference for PubMed record(s): 31088857. Abstract Here we present IPSA, an innovative web-based spectrum annotator that visualizes and characterizes peptide tandem mass spectra. A tool for the scientific community, IPSA can visualize peptides collected using a wide variety of experimental and instrumental configurations. Annotated spectra are customizable via a selection of interactive features and can be exported as editable scalable vector graphics to aid in the production of publication-quality figures. Single spectra can be analyzed through provided forms, while multiple peptide spectral matches can be uploaded directly to the server as CSV, MGF, or mzML files. IPSA facilitates the characterization of experimental MS/MS performance through the optional export of fragment ion statistics from one to many peptide spectral matches. This resource is made freely accessible at http://interactivepeptidespectralannotator.com, and the source code is available for inspection at https://github.com/dbrademan/IPSA-dev for custom implementations. This repository contains the raw data, sequence databases, and peptide identifications utilized in the manuscript.