Web IDL is an interface description language (IDL) format for describing application programming interfaces (APIs) that are intended to be implemented in web browsers. Its adoption was motivated by the desire to improve the interoperability of web programming interfaces by specifying how languages such as ECMAScript should bind these interfaces.
Web IDL is an IDL variant with:
The first edition of the Web IDL specification became a Candidate Recommendation on 19 April 2012 and a W3C Recommendation on 15 December 2016. For many years the Editor's Draft of a potential second edition, was what most new web specifications referenced. On 5 October 2021, the Editor's Draft was moved to the WHATWG as the Web IDL Living Standard per an update to the agreement between the W3C and WHATWG.