ECMAScript version history

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

Edition	Date published	Name	Changes from prior edition	Editor
1	June 1997		First edition based on JavaScript 1.1 as implemented in Netscape Navigator 3.0.	Guy L. Steele Jr.
2	June 1998		Editorial changes to keep the specification fully aligned with ISO/IEC 16262:1998.	Mike Cowlishaw
3	December 1999		Based 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 enhancements	Mike Cowlishaw
4	Abandoned	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.
5	December 2009		Adds "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
5.1	June 2011		Changes to keep the specification fully aligned with ISO/IEC 16262:2011.	Pratap Lakshman, Allen Wirfs-Brock
6	June 2015	ECMAScript 2015	See #6th edition – ECMAScript 2015	Allen Wirfs-Brock
7	June 2016	ECMAScript 2016	See #7th edition – ECMAScript 2016	Brian Terlson
8	June 2017	ECMAScript 2017	See #8th edition – ECMAScript 2017	Brian Terlson
9	June 2018	ECMAScript 2018	See #9th edition – ECMAScript 2018	Brian Terlson
10	June 2019	ECMAScript 2019	See #10th edition – ECMAScript 2019	Brian Terlson, Bradley Farias, Jordan Harband
11	June 2020	ECMAScript 2020	See #11th edition – ECMAScript 2020	Jordan Harband, Kevin Smith
12	June 2021	ECMAScript 2021	See #12th edition – ECMAScript 2021	Jordan Harband, Shu-yu Guo, Michael Ficarra, Kevin Gibbons
13	June 2022	ECMAScript 2022	See #13th edition – ECMAScript 2022	Shu-yu Guo, Michael Ficarra, Kevin Gibbons
14	June 2023	ECMAScript 2023	See #14th edition – ECMAScript 2023	Shu-yu Guo, Michael Ficarra, Kevin Gibbons
15	June 2024	ECMAScript 2024	See #15th edition – ECMAScript 2024	Shu-yu Guo, Michael Ficarra, Kevin Gibbons
16	June 2025	ECMAScript 2025	See #16th edition – ECMAScript 2025	Shu-yu Guo, Michael Ficarra, Kevin Gibbons
17		ECMAScript 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:

classes,
a module system,
optional type annotations and static typing, probably using a structural type system,
generators and iterators,
destructuring assignment, and
algebraic data types.

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.