ECMAScript version history


ECMAScript is a JavaScript standard developed by Ecma International.[] Since 2015, major versions have been published every June.
ECMAScript 2025, the 16th and current version, was released in June 2025.

Versions

EditionDate publishedNameChanges from prior editionEditor
1June 1997First edition based on JavaScript 1.1 as implemented in Netscape Navigator 3.0.Guy L. Steele Jr.
2June 1998Editorial changes to keep the specification fully aligned with ISO/IEC 16262:1998.Mike Cowlishaw
3December 1999Based on JavaScript 1.2 as implemented in Netscape Navigator 4.0. Added regular expressions, better string handling, new control statements, try/catch exception handling, tighter definition of errors, formatting for numeric output, and other enhancementsMike Cowlishaw
4Abandoned ECMAScript 4 The 4th edition was abandoned due to political differences concerning language complexity. Many features proposed for the 4th edition have been completely dropped; some were incorporated into the sixth edition.
5December 2009Adds "strict mode", a subset intended to provide more thorough error checking and avoid error-prone constructs. Clarifies many ambiguities in the 3rd edition specification, and accommodates behavior of real-world implementations that differed consistently from that specification. Adds some new features, such as getters and setters, library support for JSON, and more complete reflection on object properties.Pratap Lakshman, Allen Wirfs-Brock
5.1June 2011Changes to keep the specification fully aligned with ISO/IEC 16262:2011.Pratap Lakshman, Allen Wirfs-Brock
6June 2015ECMAScript 2015 See #6th edition – ECMAScript 2015Allen Wirfs-Brock
7June 2016ECMAScript 2016 See #7th edition – ECMAScript 2016Brian Terlson
8June 2017ECMAScript 2017 See #8th edition – ECMAScript 2017Brian Terlson
9June 2018ECMAScript 2018 See #9th edition – ECMAScript 2018Brian Terlson
10June 2019ECMAScript 2019 See #10th edition – ECMAScript 2019Brian Terlson, Bradley Farias, Jordan Harband
11June 2020ECMAScript 2020 See #11th edition – ECMAScript 2020Jordan Harband, Kevin Smith
12June 2021ECMAScript 2021 See #12th edition – ECMAScript 2021Jordan Harband, Shu-yu Guo, Michael Ficarra, Kevin Gibbons
13June 2022ECMAScript 2022 See #13th edition – ECMAScript 2022Shu-yu Guo, Michael Ficarra, Kevin Gibbons
14June 2023ECMAScript 2023 See #14th edition – ECMAScript 2023Shu-yu Guo, Michael Ficarra, Kevin Gibbons
15June 2024ECMAScript 2024 See #15th edition – ECMAScript 2024Shu-yu Guo, Michael Ficarra, Kevin Gibbons
16June 2025ECMAScript 2025 See #16th edition – ECMAScript 2025Shu-yu Guo, Michael Ficarra, Kevin Gibbons
17ECMAScript 2026 Pending, see features being considered: #ES.Next

In June 2004, Ecma International published ECMA-357 standard, defining an extension to ECMAScript, known as ECMAScript for XML. Ecma also defined a "Compact Profile" for ECMAScript – known as ES-CP, or ECMA 327 – that was designed for resource-constrained devices, which was withdrawn in 2015.

4th edition (abandoned)

The proposed 4th edition of ECMA-262 would have been the first major update to ECMAScript since the 3rd edition was published in 1999. The specification was originally targeted for completion by October 2008. The first draft was dated February 1999. An overview of the language was released by the working group on 23 October 2007.
By August 2008, the ECMAScript 4th edition proposal had been scaled back into a project code named ECMAScript Harmony. Features under discussion for Harmony at the time included:
The intent of these features was partly to better support programming in the large, and to allow sacrificing some of the script's ability to be dynamic to improve performance. For example, Tamarin – the virtual machine for ActionScript, developed and open-sourced by Adobe – has just-in-time compilation support for certain classes of scripts.
In addition to introducing new features, some ES3 bugs were proposed to be fixed in edition 4. These fixes and others, and support for JSON encoding/decoding, have been folded into the ECMAScript, 5th Edition specification.
Work started on Edition 4 after the ES-CP specification was completed, and continued for approximately 18 months where slow progress was made balancing the theory of Netscape's JavaScript 2 specification with the implementation experience of Microsoft's JScript.NET. After some time, the focus shifted to the ECMAScript for XML standard. The update has not been without controversy. In late 2007, a debate between Eich, later the Mozilla Foundation's CTO, and Chris Wilson, Microsoft's platform architect for Internet Explorer, became public on a number of blogs. Wilson cautioned that because the proposed changes to ECMAScript made it backwards incompatible in some respects to earlier versions of the language, the update amounted to "breaking the Web", and that stakeholders who opposed the changes were being "hidden from view". Eich responded by stating that Wilson seemed to be "repeating falsehoods in blogs" and denied that there was attempt to suppress dissent and challenged critics to give specific examples of incompatibility. He pointed out that Microsoft Silverlight and Adobe AIR rely on C# and ActionScript 3 respectively, both of which are larger and more complex than ECMAScript Edition 3.

5th edition – ECMAScript 2009

Yahoo, Microsoft, Google, and other 4th edition dissenters formed their own subcommittee to design a less ambitious update of ECMAScript 3, tentatively named ECMAScript 3.1. This edition would focus on security and library updates, with a large emphasis on compatibility. After the aforementioned public sparring, the ECMAScript 3.1 and ECMAScript 4 teams agreed on a compromise: the two editions would be worked on, in parallel, with coordination between the teams to ensure that ECMAScript 3.1 remains a strict subset of ECMAScript 4 in both semantics and syntax.
However, the differing philosophies in each team resulted in repeated breakages of the subset rule, and it remained doubtful that the ECMAScript 4 dissenters would ever support or implement ECMAScript 4 in the future. After over a year since the disagreement over the future of ECMAScript within the Ecma Technical Committee 39, the two teams reached a new compromise in July 2008: Brendan Eich announced that Ecma TC39 would focus work on the ECMAScript 3.1 project with full collaboration of all parties, and vendors would target at least two interoperable implementations by early 2009. In April 2009, Ecma TC39 published the "final" draft of the 5th edition and announced that testing of interoperable implementations was expected to be completed by mid-July. On 3 December 2009, ECMA-262 5th edition was published.
Additions include JSON, String.trim to easily remove whitespaces surrounding a string, String.charAt to return a single character from a given position in a string, and Array.isArray. A comma after the final pair of values in an object also no longer causes a syntax error.

6th edition – ECMAScript 2015

The 6th edition, ECMAScript 6 and later renamed to ECMAScript 2015, was finalized in June 2015. This update adds significant new syntax for writing complex applications, including class declarations, ES6 modules like import * as moduleName from "..."; export const Foo, but defines them semantically in the same terms as ECMAScript 5 strict mode. Other new features include iterators and for...of loops, Python-style generators, arrow function expression, let keyword for local declarations, const keyword for constant local declarations, binary data, typed arrays, new collections, promises, number and math enhancements, reflection, proxies and template literals using backticks for multi-line strings without escape characters. The complete list is extensive. As the first "ECMAScript Harmony" specification, it is also known as "ES6 Harmony".

7th edition – ECMAScript 2016

The 7th edition, or ECMAScript 2016, was finalized in June 2016. Its features include exponentiation operator ** for numbers, await, async keywords for asynchronous programming, and the function. The exponentiation operator is equivalent to, but provides a simpler syntax similar to languages like Python, F#, Perl, and Ruby. async / await was hailed as an easier way to use promises and develop asynchronous code.

8th edition – ECMAScript 2017

The 8th edition, or ECMAScript 2017, was finalized in June 2017. Its features include the, and functions for easy manipulation of Objects, async / await constructions that use generators and promises, and additional features for concurrency and atomics. It also includes String.prototype.padStart.

9th edition – ECMAScript 2018

The 9th edition, or ECMAScript 2018, was finalized in June 2018. New features include the spread operator and rest parameters for object literals, asynchronous iteration, Promise.prototype.finally and additions to RegExp.
The spread operator allows for the easy copying of object properties, as shown below.
let object =
let objectClone = Object.assign // before ES2018
let objectClone = // ES2018 syntax
let otherObject =
console.log // ->

10th edition – ECMAScript 2019

The 10th edition, or ECMAScript 2019, was published in June 2019. Added features include, but are not limited to, Array.prototype.flat, Array.prototype.flatMap, changes to Array.sort, and Object.fromEntries.
is now guaranteed to be stable, meaning that elements with equal sorting keys will not change relative order before and after the sort operation. Array.prototype.flat flattens an array to a specified depth, meaning that all subarray elements are concatenated recursively.
Another notable change is that so-called catch binding became optional.

11th edition – ECMAScript 2020

The 11th edition, or ECMAScript 2020, was published in June 2020. In addition to new functions, this version introduces a BigInt primitive type for arbitrary-sized integers, the nullish coalescing operator, and the globalThis object.
BigInts are created either with the constructor or with the syntax, where "n" is placed after the number literal. BigInts allow the representation and manipulation of integers beyond, while Numbers are represented by a double-precision 64-bit IEEE 754 value. The built-in functions in are not compatible with BigInts; for example, exponentiation of BigInts must be done with the operator instead of.
The nullish coalescing operator,, returns its right-hand side operand when its left-hand side is or. This contrasts with the operator, which would return for all "falsy" values, such as the ones below.
undefined ?? "string" // -> "string"
null ?? "string" // -> "string"
false ?? "string" // -> false
NaN ?? "string" // -> NaN

Optional chaining makes it possible to access the nested properties of an object without having an AND check at each level. An example is. If any of the properties are not present, will be.

12th edition – ECMAScript 2021

The 12th edition, ECMAScript 2021, was published in June 2021. This version introduces the method for strings;, a promise combinator that short-circuits when an input value is fulfilled;, a new error type to represent multiple errors at once; logical assignment operators ;, for referring to a target object without preserving it from garbage collection, and, to manage registration and unregistration of cleanup operations performed when target objects are garbage collected; separators for numeric literals ; and was made more precise, reducing the number of cases that result in an implementation-defined sort order.

13th edition – ECMAScript 2022

The 13th edition, ECMAScript 2022, was published in June 2022. This version introduces top-level, allowing the keyword to be used at the top level of modules; new class elements: public and private instance fields, public and private static fields, private instance methods and accessors, and private static methods and accessors; static blocks inside classes, to perform per-class evaluation initialization; the syntax, to test for presence of private fields on objects; regular expression match indices via the flag, which provides start and end indices for matched substrings; the property on objects, which can be used to record a causation chain in errors; the method for Strings, Arrays, and TypedArrays, which allows relative indexing; and, a convenient alternative to.

14th edition – ECMAScript 2023

The 14th edition, ECMAScript 2023, was published in June 2023. This version introduces the toSorted, toReversed, with, findLast, and findLastIndex methods on Array.prototype and TypedArray.prototype, as well as the toSpliced method on Array.prototype; added support for #! shebang comments at the beginning of files to better facilitate executable ECMAScript files; and allowed the use of most Symbols as keys in weak collections.

15th edition – ECMAScript 2024

The 15th edition, ECMAScript 2024, was published in June 2024. This version introduces the Object.groupBy and Map.groupBy static methods, Promise.withResolvers, various set operations on Set.prototype, and the /v unicode flag for regular expressions.
The Object.groupBy and Map.groupBy methods group an iterable collection using the return value of a provided callback function.
// sample data
const arr = ;
const obj = Object.groupBy;
console.log;
//
Promise.withResolvers provides a simple way to get a promise's resolve and reject functions directly without having to assign them in the constructor.
// ES 2023
let resolve;
let reject;
let promise = new Promise;
// ES 2024
const = Promise.withResolvers;
The /v flag in regular expressions is simply an improved version of the /u flag, but as it makes backwards-incompatible changes it had to be introduced as a new flag.

16th edition – ECMAScript 2025

The 16th edition of ECMAScript released in 2025. It adds the following:
  • The object which can wrap iterators like and provides a functional interface with lazy evaluation.
  • : call a method which may or may not be a promise as a promise
  • New methods:,,,,,
  • function to escape a string so it can be concatenated together with a regex pattern.
  • Importing JSON files directly as modules
  • Float16Array along with related TypedArray methods

ES.Next

ES.Next is a dynamic name that refers to whatever the next version is at the time of writing. ES.Next features include finished proposals as listed at that are not part of a ratified specification. The language committee follows a "living spec" model, so these changes are part of the standard, and ratification is a formality.

JavaScript 1.0

  • As implemented in Netscape Navigator 2.0 before submitting the first version for standardization as Ecmascript:

ISO standards

ECMA standards

  • * 1st edition, June 1997:
  • * 2nd edition, August 1998:
  • * 3rd edition, December 1999:
  • * 3rd edition, March 2000:
  • * 4th edition :
  • * 4th edition :,
  • * 5th edition, December 2009:
  • * 5.1 edition, June 2011:,
  • * 6th edition, June 2015 :,
  • * 7th edition, June 2016 :,
  • * 8th edition, June 2017 :,
  • * 9th edition, June 2018 :,
  • * 10th edition, June 2019 :,
  • * 11th edition, June 2020 :,
  • * 12th edition, June 2021 :,
  • * 13th edition, June 2022 :,
  • * 14th edition, June 2023 :,
  • * 15th edition, June 2024 :,