Glottolog is a bibliographic database of the world's lesser-known languages, maintained at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. There are two components: Languoid catalogue, the catalog of the world's languages and language families; and Langdoc, the bibliography. It differs from the better-known Ethnologue in several ways, in that it attempts only to accept languages which the editors have been able to confirm both exist and are distinct (varieties which have not been confirmed, but are inherited from another source, are tagged as "spurious" or "unattested"); it attempts only to classify languages into families which have been demonstrated to be valid; extensive bibliographic information is provided, especially for lesser-known languages; and, to a limited extent, alternative names are listed according to the sources which use them. In some cases, the language names used in the bibliographic entries in Langdoc are identified by ISO or Glottolog code; this is an area of ongoing expansion. Glottolog differs in several negative ways as well: Notably, apart from a single point-location on a map at its geographic center, no ethnographic or demographic information is provided. External links are provided to ISO, Ethnologue, and other online language databases.
Edition 2.2 was published online in 2013, and licensed under a Creative Commons Attribution-Sharealike 3.0 Unported License. Edition 2.4 was published in 2015.
Glottolog is more conservative in its classification than most online databases in establishing membership of languages and groups within families, but more liberal in considering unclassified languages to be isolates. Edition 2.4 lists 425 oral-language families, including isolates, and 75 sign-language families and isolates, as follows.
Creoles are classified with the language that supplied their basic lexicon.
In addition to languages classified into families, Glottolog recognizes 79 pidgins (including one sign pidgin), 24 mixed languages, 8 artificial languages, 9 speech registers (including 3 auxiliary sign systems), 118 attested but unclassifiable languages (including 2 sign languages), 61 unattested languages, and 270 spurious languages (such as retired ISO entries, and including 3 sign languages) kept for bookkeeping purposes.