Why is ES6 also called ES2015?

ES6 was the sixth edition of the ECMAScript standard, ratified in June 2015. From that release onward TC39 switched to a yearly cadence and named editions by their year, so ES6 is officially ES2015, ES7 is ES2016, and so on. Both names refer to the same standard.

What was the biggest ECMAScript release?

ES2015 (ES6) was by far the largest single release. It introduced let and const, arrow functions, classes, template literals, destructuring, promises, modules, Map and Set, symbols, iterators and generators. Every later edition has been comparatively incremental.

When did async/await arrive?

async and await were standardized in ES2017 (the 8th edition). They build on the promises introduced in ES2015 and let asynchronous code be written in a synchronous-looking style. The same edition added Object.values, Object.entries and string padding methods.

ES2025 added iterator helpers (map, filter, take, drop on iterators), new Set methods like union and intersection, JSON import attributes, Promise.try, RegExp.escape, Float16Array, and support for duplicate named capture groups across regex alternatives.

How does a feature get into ECMAScript?

Features go through the TC39 proposal process across four stages. A proposal must reach Stage 4 — with two independent implementations and passing test262 tests — before it is merged into the next yearly edition. The year shown here is when each feature reached Stage 4 ratification.

ECMAScript Versions Reference

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ECMAScript is the standard that JavaScript implements, and since 2015 it has been released on a strict yearly schedule with editions named by their year. Knowing which edition introduced a feature tells you how widely it is supported and what transpile target you need. This reference lists every edition from ES5 to ES2025 with the major features each one shipped.

How it works

The first edition most developers care about is ES5 (2009), which gave us strict mode, the functional array methods and native JSON. ES2015 (ES6) was the watershed release — block scoping, arrow functions, classes, promises, modules and the Map/Set collections all arrived at once. After ES2015, TC39 adopted a yearly cadence: each June a new edition ratifies whatever proposals have reached Stage 4, the final stage of the four-stage proposal process. That is why later editions are smaller and more focused, each adding a handful of well-defined features rather than a sweeping overhaul.

A proposal only enters the standard once it has two independent implementations and passes the official test262 conformance suite, so the year shown for each edition is the year those features became part of the language, not the year they first appeared behind a flag in a single engine.

Tips and notes

Use the release year to choose a transpilation target: tools like Babel and TypeScript can down-level newer syntax for older runtimes, but features that need runtime support (such as BigInt or WeakRef) cannot be polyfilled cleanly and require an engine new enough to implement them natively. When in doubt, target one or two editions behind the current year for the broadest reach.