Digitized versions of about 7,200 copies of ancient Chinese books went online on Tuesday and can now be accessed for free by the public for pleasure or academic reference, the National Library of China announced.

Most copies came from 20 public institutions nationwide. Other than the NLC, Nanjing Library, Shandong Library and Hubei Provincial Library are also among the key custodians of ancient documents, and contributed to the project.

Wei Li, a renowned independent collector of ancient books, personally contributed eight copies to the database, setting an example for new ways private collections can serve the public via digitization.

New entries to the online platform also include pictures of stone rubbings, family genealogies and ancient Buddhist sutras.

This is the fourth release of the data since its founding in 2016, when 27,000 copies went online, following a national guideilne for the preservation of ancient books. So far, around 72,000 digitized ancient books have been entered into the database for public use.

According to a symposium in the NLC on Tuesday, general surveys of ancient books have been completed in 24 provincial-level administrative regions in China, totaling 2.6 million registered books nationwide.