The version history of ECMAScript is slightly behind the current browser implementations. Versions of ECMAScript are defined as editions 2 and 3 of the standard. Edition 1 was superseded by edition 2, which made few functional changes. There were not enough to warrant revising the level of functionality.

ECMA edition 2 is roughly equivalent to JavaScript version 1.1, minus any HTML document modeling.

ECMA edition 3 is roughly equivalent to JavaScript 1.5 and JScript 5.5.