Hello ; About the libraries that you have mentioned : > 1\. JLCPCB Assembly library\, which is open in EasyEDA\. This one belongs to the classes available in EasyEDA library and it has the parts available for assembly by JLCPCB > 2\. JLCPCB Parts library\,  which is not open in EasyEDA and cannot be used in EasyEDA or JLCPCB Assembly This is the JLCPCB library and it has also the parts available for assembly by JLCPCB so this way any user could check the part availability before proceeding for order, if you ask why we have it in EasyEDA and in JLCPCB then the answer is not all users are designing their PCBs using EasyEDA so we must consider this. > 3\. JLCPCB Your parts library which is pre\-purchased inventory\. You can use the symbols\, footprints and inventory in EasyEDA and JLCPCB Assembly\. This one is meant to allow users to secure their parts for regular orders, so they create their own parts library where they stock parts that they can use for assembly whenever they need them. more details in this link : [https://support.jlcpcb.com/article/151-how-to-build-your-own-parts-library-in-jlcpcb](https://support.jlcpcb.com/article/151-how-to-build-your-own-parts-library-in-jlcpcb)<br> <br> Please let me know if you have any other questions.