- jQuery 4.0 is the first major version in nearly 10 years, coinciding with the library's 20th anniversary.
- Support for Internet Explorer 10 and older browsers is dropped, while IE 11 remains supported until jQuery 5.0.
- The source code has migrated from AMD to ES modules, and the slim build is now around 19.5 KB gzipped.
- Trusted Types support and adherence to W3C focus event standards improve security and cross-browser consistency.
The jQuery team has officially released version 4.0 of the iconic JavaScript library, marking the first major update in almost a decade. This release arrives just as the library celebrates its 20th anniversary since its initial launch on January 14, 2006. jQuery 4.0 brings extensive modernizations while maintaining the simplicity and developer experience that made it a staple of web development. The team has focused on trimming legacy code, removing deprecated APIs, and dropping support for outdated browsers, resulting in a leaner and more performant library.
According to lead developer Timmy Willison, most users should be able to upgrade with minimal changes to their code, supported by a comprehensive upgrade guide and an updated jQuery Migrate plugin. The library is available via the jQuery CDN and npm (npm install jquery@4.0.0), and the project has switched from RequireJS to Rollup for packaging. The community reaction has been largely positive, with many developers appreciating the removal of old workarounds that are no longer necessary in modern browsers.
Browser Support and Breaking Changes
One of the most significant changes in jQuery 4.0 is the removal of support for Internet Explorer 10 and older browsers, including Edge Legacy, iOS versions earlier than the last three, and the Android Browser. Internet Explorer 11 remains supported in this release, though the team has indicated that support will be removed in jQuery 5.0. These changes have allowed the library to shed over 3 kilobytes of gzipped code, making it smaller and faster. The slim build, which removes Deferreds and Callbacks, has been further reduced to around 19.5 KB gzipped, as native Promises are now available across all supported browsers except IE 11.
Modernization: ES Modules and Trusted Types
The library source code has been migrated from AMD to ES modules, making jQuery compatible with modern build tools and development workflows. Developers can now import jQuery directly as ES modules through the use of <script type="module"> tags. Additionally, jQuery 4.0 adds support for Trusted Types, ensuring that HTML wrapped in TrustedHTML can be used as input to jQuery manipulation methods without violating Content Security Policy (CSP) directives. The team has also switched most asynchronous script requests to use <script> tags rather than inline scripts to avoid CSP errors.
Removed APIs and Focus Event Changes
Several deprecated functions have been removed, including jQuery.isArray, jQuery.parseJSON, jQuery.trim, and jQuery.now, as modern browsers now provide native equivalents like Array.isArray(), JSON.parse(), String.prototype.trim(), and Date.now(). Internal array methods such as push, sort, and splice are no longer part of the jQuery prototype and now behave strictly like native array functions. In terms of event handling, jQuery 4.0 no longer overrides the native behavior of focus and blur events; instead, it adheres to the current W3C specification, which may affect existing event logic but ensures consistent behavior across all supported browsers.
Community feedback on HackerNews and Reddit has highlighted that jQuery’s code remains “shorter, cleaner, and more intuitive than the vanilla modern JS” alternatives. Many developers still rely on jQuery for maintaining large existing codebases, progressive enhancement, server-rendered sites, and small interactive behaviors without the overhead of a full framework. The library’s stability and predictability in an ecosystem of rapidly changing frameworks continue to be valued. With version 4.0, jQuery proves it is still a practical choice for many scenarios, and its 20-year legacy shows no signs of fading away.
