The collection consists of approx. 1.4 million volumes, approx. 3000 serial periodicals (newspapers, magazines and periodicals). Approx. 2,482,000 books are borrowed annually (2016).
Deichman is based on a bequest to the city from Counsellor Carl Deichman (1705-80), a book collection of 6,069 volumes, all but approx. 200 of which have been preserved intact, as well as a collection of manuscripts. The lending library was opened to the public on 12 January 1785. The donation gave rise to considerable interest and pleasure, as at the time there were no public collections of books and no university in the city. A number of the country’s most prominent figures gave their contribution in the form of book donations of various sizes. Most valuable were the 1,300 volumes (including a number of old medical works) bequeathed by chief auctioneer Johan Fredrik Bartholin (d. 1784). One of the teachers at the grammar school, later headmaster Jacob Rosted, took on the job of librarian and for this he received 50 rix-dollars a year from the school coffers. The library was located at Overhoffrettens gård, Rådhusgata 13, and it was here that the official opening ceremony took place..
In 1803, the library moved to Katedralskolen in Dronningens gate, and it moved with the school when the Norwegian Parliament made use of the premises. In 1826, the library opened at Tollbugata 1b (now Fred. Olsens gate 2). In 1840-45, the books were packed in crates until the library re-opened in the building of Borgerskolen at Kongens gate 22.Between 1845 and 1879, the library was still on the move; in 1879, it had rooms on the top floor of Studentersamfundets Hus at Universitetsgata 26; in 1894–1933 at Kristian IV's gate 8–10, and in 1933 it acquired its own building at Hammersborg (arch. Nils Reiersen). It is in the neo-classicist style. Facingt Schandorffs gate there is a tall loggia which was the beginning of a stage of the building that was not realised. In the main hall, the end wall is decorated with a fresco by Axel Revold, ‘Technolocy, Science, Literature’, dating from 1932. A new wing to the east was opened in 1972.
In 1914 the Deichman Library acquired a branch building on Schous plass (arch. August Nielsen).
EA new main library in Oslo – Nye Deichman – will open in Bjørvika in 2020. The building at was put on sale in 2019.