Tony Wang6 min readThe Bigger a Next.js Site Gets, the More Likely It's Still Running jQuery
7.85% of Next.js sites in our census still load jQuery, and the ones that do average a better traffic rank than the ones that don't.
Migrating a site from jQuery to React sounds like a clean before-and-after story: old code out, new framework in. Split our census by exactly that pairing and the story that shows up isn't a migration in progress at all — it's dependency debt, and it gets worse the bigger and more established a site gets, not better.
It isn't a React story. It's a Next.js story.
5,231 sites in this census carry both jQuery and React — enough to read as "apps caught mid-migration between an old library and a new framework." But almost two-thirds of them (62.0%) also run Next.js specifically, not bare React. A site running Next.js already has React bundled in as a dependency of the framework itself, so a large share of what looks like "jQuery+React coexistence" is really "a Next.js site that has also, somewhere, picked up jQuery" — a meaningfully different phenomenon than an app slowly rewriting itself away from an older library.
Half of it has a name
Three specific libraries explain a meaningful chunk of the pattern on their own. Bootstrap — whose JavaScript components required jQuery in every version before 5.0 — appears on 992 of the 3,245 jQuery+Next.js sites. Webflow, the no-code site builder, ships jQuery in every site it exports or hosts, and shows up on 488. jQuery UI, itself a jQuery-dependent widget library, appears on 312. Together, at least one of these three explains 1,571 of the 3,245 sites — 48.4%, essentially half. The remaining 51.6% isn't explained by any single library at this scale; it's spread across whatever else a given site has bolted on over time — an older analytics snippet, a specific ad network's embed, a widget from a vendor that hasn't updated its own script since 2015. There's no second smoking gun here, and that's itself part of the finding: once you get past the three obvious culprits, jQuery's presence on a modern framework isn't one habit, it's a hundred small ones.
The direction runs backwards from the obvious guess
If jQuery-on-Next.js read as "a smaller, less-maintained site that never got around to a full cleanup," you'd expect those sites to skew toward the long tail. They don't — they skew the other way. Sites carrying both jQuery and Next.js average a rank of 358,480; Next.js sites with no jQuery at all average 415,209, noticeably deeper in the tail. Bigger, more established, higher-traffic sites are more likely to be the ones still carrying jQuery alongside a modern framework, not less. That's consistent with the dependency-debt read: a bigger organization has had more time to accumulate more third-party integrations, more vendor widgets, more legacy code paths that never got a green light to remove — even after the core framework itself gets modernized. Migrating the framework turns out to be the easy part; migrating every dependency that framework's predecessor ever accumulated is the part that never quite finishes.
Overall, 7.85% of every Next.js site in this census (3,245 of 41,336) still loads jQuery somewhere on its homepage.
Limits, stated plainly
This is a homepage-only, same-page co-occurrence measurement — it can't distinguish jQuery genuinely wired into the page's own interactivity from jQuery loaded once by a single third-party widget and never touched again, and it can't see whether a site's engineering team is actively planning a cleanup or has simply never prioritized one. "Explained by Bootstrap/Webflow/jQuery UI" means those libraries are present on the same page, not a confirmed causal chain proving they're the reason jQuery loads. And as with the rank-tier findings elsewhere in this census, correlation with a better average rank doesn't mean carrying jQuery causes more traffic — the more likely direction of causality is the reverse: bigger, older organizations accumulate more legacy dependencies simply by having existed and integrated more vendors for longer.
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1,000,000 fingerprinted domains — CDN, CMS, ecommerce, analytics, JavaScript framework and more — over one REST API, ranked by Tranco traffic rank.
Frequently asked questions
Do Next.js sites still load jQuery?
Yes - 7.85% of all Next.js sites in Crawlora's 1,000,000-domain tech-stack census (3,245 of 41,336) still load jQuery somewhere on the homepage, despite Next.js bundling React and having no dependency on jQuery itself.
Is jQuery+React coexistence really about apps migrating away from jQuery?
Mostly not. Of 5,231 sites running both jQuery and React, 62.0% (3,245) also run Next.js specifically - meaning most of what looks like 'jQuery+React coexistence' is really 'a Next.js site that has also picked up jQuery,' not a bare React app slowly replacing an older jQuery codebase.
What's pulling jQuery onto modern Next.js sites?
About half of it traces to three identifiable libraries: Bootstrap (992 of 3,245 jQuery+Next.js sites - pre-v5 Bootstrap required jQuery), Webflow (488 sites - ships jQuery in every export), and jQuery UI (312 sites, itself a jQuery-dependent widget library). Combined, these three explain 48.4% of the pattern; the remaining 51.6% is a long tail of individual third-party embeds with no single dominant cause.
Do bigger or smaller websites carry more legacy jQuery dependency?
Bigger ones, on average - the opposite of the obvious guess. Sites running both jQuery and Next.js average a Tranco rank of 358,480, better than the 415,209 average for Next.js sites with no jQuery at all. More established organizations appear to accumulate more legacy third-party dependencies over time, even after modernizing their core framework.