AC Online is straightforward to use, presenting the equivalent of a 1,000-page book in four main sections.

Under Background appear an Historical overview and a lengthy bibliographic guide to using the resource, entitled Explaining the Annotated Catalogue. The Historical overview is itself divided into several sections – Legal contexts, General characteristics of Chopin’s first editions, and Chopin’s publishers – with subordinate categories in each case. A similar arrangement is adopted for Explaining the Annotated Catalogue.

The Catalogue constitutes the heart of the resource, with individual entries on its c. 2,000 constituent sources. These are organised in five sections. The first two categories – Works with opus numbers, and Works without opus numbers – include descriptions of first editions which appeared during Chopin’s lifetime. The third and fourth categories – Posthumous works with opus numbers, and Posthumous works without opus numbers – present similar descriptions but for editions published after the composer’s death in 1849. The last category – All works – comprises every piece in the resource. When a given work is selected, a list of the available impressions appears below. Details of these can be seen in turn by clicking on the relevant edition/impression code (see Glossary). The details appear within a PDF ‘snippet’ which can be viewed more clearly by clicking on it. Where available, links to external websites (e.g. Chopin Early Editions and POLONA) appear for individual copies so that users can inspect the actual editions under discussion. At the bottom of the ‘snippet’ webpage are links to the CFEO and/or OCVE when digital images of the source in question can be found in one or both sites; these links do not appear on the screen otherwise.

The Appendices expand on the abbreviated descriptions presented in respective catalogue entries (Appendices I & II), synthesise relevant material (Appendix III), or reproduce select digital images which to date have not been located on external websites (Appendix V). The first two Appendices are organised by the names of publishers, while Appendix III provides information about libraries and private collections in an integral list and also arranged by city and by country. When links are selected from within Appendix III, details of the specific impressions catalogued within the resource are shown. Finally, Appendix IV presents information about works which have not been catalogued.

The fourth main section comprises different types of Reference material, namely Bibliography, Glossary, List of abbreviations, and Sigla of publishers.

Navigation throughout AC Online has been designed with ease of use and maximum efficiency in mind. The main sections are shown in the green banner at the top, with the lower banner displaying subordinate sections, including the one being displayed on the screen. The sidebar also indicates relevant high-level categories.

Numerous internal  links are provided to other areas of the ACO resource or to external sites, in the latter case enabling comparison of the descriptions in ACO with the original material on which they are based. Such links are generally indicated by green lettering, although external links within PDF-based catalogue entries appear in blue and are underlined.

Additional information about the use of the resource is presented in Explaining the Annotated Catalogue, which users are advised to read carefully in order to understand and utilise the contents of AC Online to best advantage.