Web IDL is an interface description language (IDL) format for describing APIs (application programming interfaces) that are intended to be implemented in web browsers.
[3] However, interfaces defined using OMG IDL were not able to specify behavior for JavaScript precisely, leading to issues with interoperability.
[3][1] WebIDL improved on this status quo by providing data types and binding specifications that make the intended behavior in JavaScript clearer.
[4] 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.