OCA is an open format to ease the exchange of traditionnal/frame-by-frame/cel animation between different applications.
To Export to the OCA format, go to Tools ‣ Scripts ‣ OCA Export.
To learn more about OCA, visit rxlaboratory.org.
To learn how to use the OCA exporter for Krita and what it can do, visit oca-krita.rxlab.guide.