After 10 Years, jQuery 4.0 Modernizes Legacy Web Development

Remember the mid-2010s? Everyone was writing $(document).ready() like it was a religious ritual. jQuery was everywhere powering WordPress themes, corporate intranets, e-commerce checkouts, and pretty much every website that wasn't hand-coded in vanilla JavaScript by someone trying to prove a point.

Then came React, Vue, Angular and jQuery quietly became the thing developers apologized for using. "We still have jQuery in the codebase," someone would mumble in a standup, the way you'd admit to still owning a flip phone.

But here's the thing: jQuery never actually died. It just kept working. Quietly. Reliably. On billions of websites.

And now, after nearly a decade of incremental updates, jQuery 4.0 has officially arrived and it's not just a patch. It's a proper, thoughtful modernization that deserves more attention than it's getting.

So What Took So Long?

Fair question. jQuery 3.0 dropped back in 2016. That's a long time in web years, practically the Jurassic period.

The jQuery team wasn't sitting idle, though. The challenge with a library this widely used is that every change you make breaks something for someone. jQuery runs on an estimated 77% of the top 10 million websites (yes, still). When your code touches that much of the internet, you don't move fast and break things. You move carefully and try not to break the internet.

jQuery 4.0 is the result of years of careful, deliberate decisions, stripping out the dead weight while staying true to what made jQuery great in the first place: simplicity, readability, and cross-browser reliability.

What Actually Changed in jQuery 4.0?

Let's get into the good stuff without turning this into a technical whitepaper.

Internet Explorer Is Finally Gone

This is the big one. jQuery 4.0 officially drops support for Internet Explorer. All of it. IE 9, IE 10, IE 11 gone.

For years, a huge chunk of jQuery's source code existed purely to smooth over Internet Explorer's various quirks and crimes against web standards. Removing IE support meant the team could delete enormous amounts of compatibility code, making the library leaner and faster.

If you're still building for IE at this point... we need to have a different conversation.

Promises That Actually Behave Like Promises

jQuery had its own Deferred objects for handling asynchronous code and they were fine, mostly. But they didn't follow the standard Promises/A+ specification that the rest of the JavaScript world uses.

jQuery 4.0 brings its Deferreds in line with native Promises. This matters because it means jQuery now plays nicely with async/await and the broader modern JavaScript ecosystem. You're no longer translating between two different async dialects.

Slim Build Gets Slimmer

jQuery already had a "slim" version that excluded certain modules. jQuery 4.0 takes this further, trimming the overall file size. In a world obsessed with Core Web Vitals and page speed scores, every kilobyte counts, especially on mobile connections.

Cleaner Event Handling

Some of jQuery's older event handling methods particularly jQuery.event.handle and certain delegation patterns have been cleaned up or removed. The result is more predictable, standards-aligned behavior.

No More .ajax() Workarounds for Modern APIs

With the Fetch API now widely supported across browsers, jQuery's AJAX utilities have been updated to align better with modern expectations. You're no longer fighting the library to do things the current way.

Why Does This Matter for Real Projects?

Here's where it gets genuinely interesting, especially if you work in custom website development. 

A lot of custom website development projects aren't greenfield applications built entirely with React. They're WordPress sites, WooCommerce builds, legacy CMS platforms, internal business tools, and hybrid applications where jQuery is already embedded deep in the stack.

For these projects, jQuery 4.0 is genuinely good news. You don't have to rip out a working foundation and rebuild everything from scratch. You can upgrade, strip out the IE compatibility band-aids you were maintaining yourself, and write cleaner, more modern code on top of a leaner library.

This is especially true for agencies and freelancers doing custom website development for small and medium businesses, the clients who need reliable, maintainable sites without the overhead of a full JavaScript framework.

"But Should I Still Use jQuery in 2026?"

Honestly? It depends on what you're building.

If you're starting a new, complex single-page application, probably reach for something purpose-built for that: React, Vue, Svelte. These frameworks handle component state, reactivity, and app architecture in ways jQuery was never designed to do.

But if you're:

  • Building or maintaining a WordPress or CMS-based site 
  • Working on a project that already depends on jQuery (and removing it would cost more than it saves) 
  • Building something simple that doesn’t require a full framework 
  • Prioritizing developer familiarity and fast delivery over architectural purity 

...then jQuery 4.0 is a perfectly reasonable, modernized choice. Don't let framework snobbery tell you otherwise.

The Upgrade Path: Is It Painful?

Moderately, depending on your codebase.

The jQuery team released a migration plugin jquery-migrate that helps identify deprecated methods in your existing code. It flags the things that will break, gives you warnings in the console, and guides you through what needs updating.

The biggest pain points will be:

  • Removed methods that you might still be calling (like .size(), which was just .length anyway)
  • Changed Ajax behavior if you relied heavily on jQuery's older async patterns
  • Event handling differences if you're doing anything particularly custom

For most projects, a combination of the migration plugin and a few hours of testing will get you there. For very large legacy codebases, it might take longer but the 3.x branch will still receive security updates for a while, so you're not under immediate pressure.

The Bigger Picture

jQuery 4.0 is a reminder that "old" doesn't mean "bad," and "modern" doesn't mean "from scratch."

The web has a long memory. Code written in 2010 is still running in production. Decisions made years ago still shape what millions of users experience every day. jQuery survived not because developers were lazy or behind the times, it survived because it solved real problems elegantly, and it kept solving them.

Version 4.0 doesn't try to compete with React or reinvent itself as something it's not. It just becomes a better version of what it always was: a fast, friendly, reliable tool for working with the DOM and making web interactions feel smooth.

That's not nothing. That's actually quite a lot.

FAQ

Q1: Is jQuery 4.0 backward compatible with jQuery 3.x?

Mostly, but not fully. jQuery 4.0 removes some deprecated methods and modifies some behaviors that were previously allowed. The official jquery-migrate plugin is the recommended way to identify compatibility issues before fully upgrading. For most projects, the migration is manageable with some testing.

Q2: Is jQuery 4.0 suitable for new projects or should we consider a modern framework?

The decision depends on the project scope. For content-heavy sites, WordPress projects, or projects that don't require advanced UI state management, jQuery 4.0 is an appropriate choice. For sophisticated single-page applications with high levels of dynamic UI, a component-based framework like React or Vue might be more suitable.

Q3: Will jQuery 4.0 be compatible with WordPress?

WordPress provides its own version of jQuery, and support for jQuery 4.0 will depend on updates to WordPress core and your theme/plugin ecosystem. It's not a drop-in replacement for WordPress's bundled jQuery yet, check plugin compatibility carefully before upgrading in a WordPress environment.

Q4: What happened to IE support, and does that matter?

jQuery 4.0 no longer supports any version of Internet Explorer. Microsoft officially stopped supporting IE 11 in June 2022, and browser usage statistics show that IE accounts for less than 0.5% of global traffic. Unless you are targeting a very specific audience (such as some government or enterprise environments), dropping IE support is a safe bet in 2024 and beyond.

Q5: Do we still need jQuery and its features with native browser APIs, such as fetch, querySelector and CSS animations?

Yes, native browser APIs have closed a lot of the gap that jQuery was originally filling. But jQuery still offers a concise, consistent syntax, better cross-browser event handling, and a massive ecosystem of plugins. It’s less necessary than it was in 2009, but it’s still genuinely useful, especially when working within existing codebases or platforms that rely on it.

 

jQuery 4.0 isn't trying to be the future of the web. It's just trying to be a more honest, cleaner version of a tool that's already shaped the web more than most people realize. And sometimes, that's exactly enough.