International Alphabet of Sanskrit Transliteration

The International Alphabet of Sanskrit Transliteration (IAST) is a popular transliteration scheme that allows a lossless romanization of Indic scripts.

Popularity
IAST is the most popular transliteration scheme for romanization of Sanskrit and Pāḷi. It is often used in printed publications, especially for books dealing with ancient Sanskrit and Pāḷi topics related to Indian religions. With the wider availability of Unicode fonts, it is also increasingly used for electronic texts.

IAST is based on a standard established by the International Congress of Orientalists at Geneva in 1894. It allows a lossless transliteration of Devanāgarī (and other Indic scripts, such as Śāradā script), and as such represents not only the phonemes of Sanskrit, but allows essentially phonetic transcription (e.g. Visarga  is an allophone of word-final r and s).

The National Library at Kolkata romanization, intended for the romanization of all Indic scripts, is an extension of IAST.

IAST sign inventory and conventions
The sign inventory of IAST (both small and capital letters) shown with Devanāgarī equivalents and phonetic values in IPA, is as follows (valid for Sanskrit; for Hindi, some minor phonological changes have occurred):    

Note: Unlike ASCII-only romanizations such as ITRANS or Harvard-Kyoto, the diacritics used for IAST allow capitalization of proper names. The capital variants of letters never occurring word-initially are only useful in  contexts, where the convention is to typeset the IT sounds as capital letters (see ).

Comparison with ISO 15919
For the most part, IAST is a subset of ISO 15919. The following five exceptions are due to the ISO standard accommodating an extended repertoire symbols to allow transliteration of Devanāgarī and other Indic scripts as used for languages other than Sanskrit.