Although the classification of conlangs depends on viewpoints of academians, conlangers and users, conlangs are approximately classified as follows.
** International auxiliary languages (IAL, Auxlangs) **
Auxlangs are made for the purpose of communications between different regions’ people or different races speaking different native languages with each other. They are the most popular conlangs among conlangers, and so many conlangers have been in fierce competition to make them regardless of whether they treat auxlangs as academics or as hobbies. However, we can find only a few auxlangs such as Esperanto or Ido that have native speakers nowadays in the 21st century.
Esperanto, Ido, Volapük, Idiom Neutral, Interlingue, Interlingua, Novial, Latino sine flexione, Globish, Basic English, Lingwa de Planeta, Earth Language, Babm, Zilengo, etc.
** Languages taking a intermediate stand between natlangs (natural languages) and conlangs **
They are often called pijin languages or creole languages.
Hebrew language (which was an ancient dead language, but has been restored artificially under religious circumstances, and has been adopted as an official language of Israel),
Bahasa Indonesia (Indonesian language, which has been evolved from the Old Malay language spoken among the traders, and has been adopted as an official language),
Filipino language (which is the artificial standardized form of Tagalog language),
協和語 (Kyowa-go, which had been spoken in Manchukuo “満州国”),
** Engineered languages (Engelangs) **
Although they are divided into subclasses such as philosophical languages, logical languages (loglangs) or experimental languages, the classification depends on viewpoints of individuals or groups, and there is no established theory. Auxlangs above and artlangs (artistic languages) below can be also divided into such subclasses.
* Philosophical languages *
They are often based on philosophical or religious convictions, and can be artlangs.
Ro, Toki Pona, Láadan, Solresol, Lingua Ignota, etc.
* Logical languages (Loglangs), formal languages *
The thoroughgoing forms of them can be called mathematics and logic themselves.
Loglan, Lojban, Ceqli, etc.
* Experimental languages *
They can be also philosophical languages, loglangs or artlangs.
Ithkuil, Epun, Europanto, etc.
** Other various auxiliary languages **
They have been made to enable us to communicate rapidly beyond limitations of physical functions and intervals, or to show or to hide information, which are often based on natlangs.
Sign languages (International sign, Japanese sign language), Braille, flag semaphore (Modern semaphore, Japanese semaphore), Morse code (International Morse code, Japanese Morse code), traffic signs, pictograms, secret languages in market spaces and stores by wholesalers, etc.
** Artistic languages (artlangs) **
Languages constructed by J. R. R. Tolkien, Klingon language (spoken in the Star Trek universe), Na'vi language (spoken in the Avatar universe), Nadsat (constructed by Anthony Burgess), etc.
** Computer languages **
Programming languages, markup languages, database languages, etc.