John Resig announced jQuery 561 at BarCamp NYC in January 2006, when every browser had its own event model and querySelectorAll() did not exist. Browsers have since standardized what jQuery papered over, yet W3Techs 13,241 still found it on 65.7% of all websites in September 2026, 78.6% of them on version 3.
jQuery 4.0.0 (MIT licence, OpenJS Foundation) arrived on January 17, 2026, the first major release since 2016. It drops IE 10 and older, Edge Legacy and the old Android Browser (IE 11 goes in jQuery 5), moves the source from AMD to ES modules, accepts Trusted Types TrustedHTML values, and removes deprecated helpers:
$.isArray(), $.isFunction(), $.type(), $.isNumeric(), $.isWindow(): use Array.isArray(), typeof and Number.isFinite().
$.trim(), $.parseJSON(), $.now(), $.camelCase(): use str.trim(), JSON.parse() and Date.now().
$.cssNumber, $.cssProps, $.fx.interval, the array methods .push(), .sort() and .splice() on jQuery sets, the toggleClass(boolean) signature and automatic JSONP promotion.
<script src="https://code.jquery.com/jquery-4.0.0.min.js"></script>
<!-- or the slim build: no AJAX, effects, Deferreds or Callbacks -->
<script src="https://code.jquery.com/jquery-4.0.0.slim.min.js"></script>The full file is 27.4 KB gzipped and the slim build 19.4 KB (npm 2,036 install jquery for bundlers). Event shorthands such as .click(fn) still work but are deprecated in favor of .on().