https://community.graphisoft.com/t5/Archicad-C-API/Old-extensions/m-p/279720#M4050 I assume you mean "add-ons"? All add-ons have to be built (compiled) specifically for each version of AC, as they utilize a variety of common information. So, you cannot simply copy an add-on from AC 20 to AC 21 and expect it to run. The developer would have to recompile it for AC 21. Fri, 30 Mar 2018 23:36:42 GMT Karl Ottenstein 2018-03-30T23:36:42Z https://community.graphisoft.com/t5/Archicad-C-API/Old-extensions/m-p/279719#M4049 <DIV class="actalk-migrated-content">Can I somehow use my old extensions in Archicad 21? Some company have their own product-specific extensions, but only for ac19, ac20, is there any possibility?</DIV> Tue, 06 Dec 2022 12:43:44 GMT https://community.graphisoft.com/t5/Archicad-C-API/Old-extensions/m-p/279719#M4049 Anonymous 2022-12-06T12:43:44Z https://community.graphisoft.com/t5/Archicad-C-API/Old-extensions/m-p/279720#M4050 I assume you mean "add-ons"? All add-ons have to be built (compiled) specifically for each version of AC, as they utilize a variety of common information. So, you cannot simply copy an add-on from AC 20 to AC 21 and expect it to run. The developer would have to recompile it for AC 21. Fri, 30 Mar 2018 23:36:42 GMT https://community.graphisoft.com/t5/Archicad-C-API/Old-extensions/m-p/279720#M4050 Karl Ottenstein 2018-03-30T23:36:42Z