|Full name||Bibliographic code|
|No. of digits||19|
The bibcode (also known as the refcode) is a compact identifier used by several astronomical data systems to uniquely specify literature references.
The Bibliographic Reference Code (refcode) was originally developed to be used in SIMBAD and the NASA/IPAC Extragalactic Database (NED), but it became a de facto standard and is now used more widely, for example, by the NASA Astrophysics Data System, which coined and prefers the term "bibcode".  
The code has a fixed length of 19 characters and has the form
YYYY is the four-digit year of the reference and
JJJJJ is a code indicating where the reference was published. In the case of a journal reference,
VVVV is the volume number,
M indicates the section of the journal where the reference was published (e.g.,
L for a letters section),
PPPP gives the starting page number, and
A is the first letter of the last name of the first author. Periods (
.) are used to fill unused fields and to pad fields out to their fixed length if too short; padding is done on the right for the publication code and on the left for the volume number and page number.
 Page numbers greater than 9999 are continued in the
M column. The 6-digit article ID numbers (in lieu of page numbers) used by the Physical Review publications since the late 1990s are treated as follows: The first two digits of the article ID, corresponding to the issue number, are converted to a lower-case letter (01 = a, etc.) and inserted into column
M. The remaining four digits are used in the page field.
Some examples of bibcodes are:
||Heintz, W. D. (1974). "Astrometric study of four visual binaries". The Astronomical Journal. 79: 819–825. Bibcode: 1974AJ.....79..819H. doi: 10.1086/111614.|
||Eddington, A. S. (1924). "On the relation between the masses and luminosities of the stars". Monthly Notices of the Royal Astronomical Society. 84 (5): 308–332. Bibcode: 1924MNRAS..84..308E. doi: 10.1093/mnras/84.5.308.|
||Kemp, J. C.; Swedlund, J. B.; Landstreet, J. D.; Angel, J. R. P. (1970). "Discovery of circularly polarized light from a white dwarf". The Astrophysical Journal Letters. 161: L77–L79. Bibcode: 1970ApJ...161L..77K. doi: 10.1086/180574.|
||Mukherjee, M.; Kellerbauer, A.; Beck, D.; et al. (2004). "The Mass of 22Mg" (PDF). Physical Review Letters. 93 (15): 150801. Bibcode: 2004PhRvL..93o0801M. doi: 10.1103/PhysRevLett.93.150801. PMID 15524861.|