Both modern and historical characters are included, as well as former and proposed IPA signs and non-IPA phonetic letters.
[3] With the ability to use Unicode for the presentation of IPA symbols, ASCII-based systems such as X-SAMPA are being supplanted.
The extIPA characters for disordered speech are additions to the IPA for phonemes that do not occur in natural languages, but are needed for recording pre-linguistic utterances by babies, gibberish from otherwise lingual individuals, and other non-linguistic but phonetic utterances.
The IPA Extensions block has been present in Unicode since version 1.0, and was unchanged through the unification with ISO 10646.
[6] The following Unicode-related documents record the purpose and process of defining specific characters in the IPA Extensions block: