The BibTeX Format

What a .bib file contains

A BibTeX file may contain four kinds of blocks, each starting with an @:

• Entries such as @article, @book or @inproceedings, each describing one reference.
• @string defines abbreviations that can be used in field values.
• @preamble holds LaTeX code that is copied into the bibliography, typically macro definitions.
• @comment is ignored by BibTeX. In practice, anything outside an @ block is ignored too.

An entry consists of the entry type (the word after @), a citation key, and a list of fields:

@misc{patashnik-bibtexing,
  author = {Oren Patashnik},
  title  = {{BibTeXing}},
  year   = {1988}
}

Entry types and field names are not case-sensitive: @ARTICLE, @Article and @article are the same. The citation key is what you use in \cite{...}. It must be unique within your files, and it’s best to stick to letters, digits and -_:. in it.

Entry types

These are the standard entry types understood by all classic BibTeX styles. Fields in the required column must be present, otherwise BibTeX prints a warning. Optional fields are used when present. Any other field is silently ignored, so you can store extra information such as abstract or keywords without affecting the output.

Every entry type also accepts key (used for sorting and labels when there is no author) and crossref. The entry types overview has a page for each of the common types, with a complete example and notes on every field.

Newer styles and biblatex add types such as @online, @software, @dataset or @thesis. Classic BibTeX styles treat unknown types like @misc. See Using BibTeX for when to choose biblatex.

Standard fields

Fields that aren’t in the classic standard but are widely used include doi, url, isbn, issn, eprint and urldate. The standard styles ignore them. natbib’s plainnat, abbrvnat and unsrtnat print doi, url, isbn and issn, and IEEEtran prints url; none of these prints eprint or urldate. The biblatex styles print all six.

Names

The author and editor fields hold one or more names separated by the word and. Never use commas to separate people. BibTeX understands three name forms:

The comma forms are unambiguous and therefore recommended. A lower-case word before the last name (van, von, de la) is recognised as a particle.

author = {Lamport, Leslie and Patashnik, Oren and Knuth, Donald E.}
author = {Lamport, Leslie and others}
author = {{World Health Organization}}

and others at the end of the list is printed as “et al.” A corporate author needs a second pair of braces. Without the extra braces, BibTeX would treat Organization as the last name of someone called World Health.

Field values

A field’s value is enclosed either in braces or in double quotes. Numbers may also stand alone. The following are equivalent:

title = {{Bib}{\TeX}}
title = "{Bib}{\TeX}"
title = "{Bib}" # "{\TeX}"

The difference between the two forms is how they nest. Inside quotes, a literal " must be wrapped in braces ({"}), and inside braces, braces must be balanced. The # operator concatenates values and @string abbreviations. Fields are separated by commas, and a comma after the last field is allowed:

@article{mrx05,
  auTHor    = "Mr. X",
  Title     = {Something Great},
  publisher = "nob" # "ody",
  YEAR      = 2005,
}

This is a correct BibTeX entry, although not a very readable one.

Abbreviations with @string

@string defines an abbreviation once and lets you reuse it anywhere a value is allowed:

@string{tugboat = {TUGboat}}
@string{btx     = {{\textsc{Bib}\TeX}}}

@article{example,
  author  = {Oren Patashnik},
  title   = btx # {ing},
  journal = tugboat,
  year    = 1988
}

Abbreviations are used without braces or quotes, and they must be defined before they are used. The month names jan to dec are predefined, and most styles also define common journal abbreviations.

@preamble and @comment

@preamble passes LaTeX code to the bibliography, which is useful for commands that your entries use:

@preamble{ "\providecommand{\noopsort}[1]{}" }

@comment blocks and any text outside @ blocks are ignored. This makes it easy to add notes to a .bib file, but be careful: a stray @ in such text starts a new block.

Cross-references

An entry can inherit fields from another entry through crossref. This is typically used for papers in the same proceedings:

@inproceedings{doe2024example,
  author   = {Doe, Jane},
  title    = {An Example Paper},
  pages    = {97--111},
  crossref = {conf2024}
}

@proceedings{conf2024,
  editor    = {Roe, Richard},
  title     = {Proceedings of the Example Conference},
  booktitle = {Proceedings of the Example Conference},
  year      = {2024},
  publisher = {Example Press}
}

The cross-referenced entry must come after the entries that refer to it. If two or more cited entries refer to it, it is also listed in the bibliography on its own (BibTeX’s -min-crossrefs option changes that threshold).