Legacy dependencies don’t usually fail loudly—they fail eventually. And when they do, it’s often at the exact moment you can least afford a surprise: a browser deprecation, a security mandate, a framework migration, or a platform refresh.
That’s why jQuery 4 landing as the first major jQuery release in almost 10 years is worth paying attention to—even if your org “moved on from jQuery” years ago. As reported by InfoQ in “jQuery Releases v4: First Major Version in Almost 10 Years”, the release is framed as a milestone in jQuery’s long history, noting roughly 20 years of the project’s longevity. That combination—everywhere adoption + long stability + a rare major bump—is a pattern many engineering leaders should recognize in their own dependency graphs.
Context: jQuery 4 as a milestone—and a mirror
jQuery became foundational because it solved real cross-browser pain and offered a clean abstraction. Over time, it also became the kind of dependency teams stop thinking about: it’s “done,” it’s “stable,” and it’s deeply embedded in templates, plugins, build pipelines, and old pages that still drive meaningful revenue.
InfoQ’s coverage positions jQuery 4 as a notable step in a project that’s been around for ~20 years and underscores that this is a major version change after nearly a decade. That matters because long gaps between major versions are common for what you might call “stable but everywhere” dependencies:
- They don’t change often, so teams pin versions and forget about them.
- They are used in many places, so upgrading feels risky.
- They accumulate subtle compatibility assumptions that aren’t documented anywhere.
When the major release finally arrives, it’s less like “a normal upgrade” and more like a dependency renaissance—suddenly everyone has to re-learn what they rely on, what was accidental, and what has to be tested.
The hidden risk of long-lived dependencies
A long time between major versions can feel like safety. In practice, it often means risk is compounding quietly.
Stability can mask “compatibility drift”
Even if a library stays stable, everything around it changes:
- Browsers ship new behaviors and deprecate old ones.
- Security baselines evolve (CSP, SRI, dependency auditing expectations).
- Tooling changes (module bundlers, transpilers, ES targets).
- Teams turn over, and institutional knowledge decays.
When you finally touch a pinned dependency, you’re not only reconciling a library change—you’re reconciling years of ecosystem drift.
“Stuck library” debt is real debt
Many orgs carry at least one pinned dependency that nobody wants to move:
- “It’s in 200 pages and a CMS theme.”
- “A vendor plugin depends on it.”
- “We tried once and it broke production.”
That’s not just technical debt; it’s operational debt. It increases the cost of:
- responding to security issues,
- adopting new platforms,
- modernizing build systems,
- and running reliable CI.
In other words: you might not be paying interest every sprint, but you’re accumulating principal that comes due when the ecosystem forces a change.
What jQuery 4 teaches about upgrade planning
If you maintain older front ends (or any mature product), jQuery 4 is a useful case study for how to plan upgrades when a dependency is both foundational and widely distributed.
1) Treat major upgrades as programs, not tickets
A major bump after years of inertia shouldn’t be scheduled as “one sprint, one PR.” It’s closer to a small program:
- inventory,
- testing work,
- phased rollout,
- rollback planning,
- stakeholder communication.
A practical approach is to plan three tracks in parallel:
- Discovery: Where is the dependency used? Which versions? Which plugins? Which pages still ship it?
- Safety net: What tests exist? What monitoring will catch regressions?
- Migration: What code changes are required and in what order?
This framing helps CTOs and engineering managers set realistic expectations: you’re not “upgrading a library,” you’re reducing systemic change risk.
2) Build a usage inventory before you touch code
Teams frequently underestimate how much they rely on legacy behavior until it breaks. Start by answering:
- Where is jQuery loaded (CDN, bundle, inline)?
- Are there multiple versions on the same page?
- Which internal modules import it?
- Which third-party plugins require it?
- Which patterns are used (DOM manipulation, AJAX, event delegation, animations)?
This is also where modernization platforms (like Vibgrate) can help: dependency graphs, code search, and repo-to-runtime mapping are most valuable before the first migration PR exists.
3) Compatibility testing is a product investment
A rare major release forces the question: what do we actually test?
If your UI test suite is thin, upgrading will feel like walking through a dark room. Make the investment explicit:
- Add smoke tests for top user journeys (login, checkout, critical CRUD flows).
- Add contract tests for shared UI components.
- Add visual regression tests for legacy pages that are heavy on DOM manipulation.
- Ensure browser coverage reflects reality (including any enterprise/embedded constraints).
One reason “stuck library” debt persists is that teams don’t trust upgrades without a safety net. Improving test coverage isn’t just for this upgrade—it’s how you make the next one cheaper.
4) Plan for plugin and transitive dependency fallout
In many jQuery-era stacks, the real constraint isn’t jQuery itself—it’s the constellation of plugins, widgets, and vendor code around it.
Create a compatibility matrix:
- Which plugins are actively maintained?
- Which have known alternatives?
- Which are bundled into vendor packages you can’t change?
Then decide explicitly:
- Upgrade (preferred): move plugin versions forward.
- Replace: swap in a maintained alternative.
- Isolate: keep legacy pages on the old dependency behind a boundary.
- Retire: remove features that no longer justify their maintenance cost.
Major releases are a rare opportunity to make these tradeoffs consciously rather than under incident pressure.
Paying down “stuck library” debt without breaking everything
Teams often swing between two extremes: “never upgrade” and “big bang rewrite.” jQuery 4 is a reminder there’s a pragmatic middle.
1) Use strangler patterns for legacy front ends
If you have a large legacy UI:
- Keep legacy pages stable.
- Build new pages or components in a modern stack.
- Gradually route traffic or navigation to the new surfaces.
The point isn’t to eliminate jQuery overnight; it’s to prevent new code from deepening the dependency while you shrink the legacy surface area.
2) Introduce a compatibility layer where it makes sense
Sometimes the fastest path is to wrap fragile usage patterns:
- centralize DOM selectors,
- standardize AJAX calls,
- create a small internal adapter for event handling.
This reduces “dependency sprawl” and makes it easier to upgrade or replace later.
3) Stage upgrades with flags and canaries
For production systems, treat major dependency upgrades like any other risky change:
- ship behind a feature flag,
- canary to internal users or a small traffic slice,
- monitor error rates and performance,
- keep rollback fast.
This is a DevOps maturity move: you’re turning a scary, one-shot release into a controlled rollout.
Practical implications for CTOs and engineering leaders
The most valuable lesson in InfoQ’s jQuery 4 story isn’t “go upgrade jQuery.” It’s that dependencies with long stable periods can create a false sense of security.
Make dependency freshness measurable
Add lightweight governance:
- Track “time since last upgrade” for foundational libraries.
- Track version skew across repos and runtime surfaces.
- Require an owner for top dependencies (not to gatekeep, but to prevent neglect).
If you can’t answer “where is jQuery used?” quickly, you have an observability problem—not just a code problem.
Put upgrades on a cadence
A good modernization strategy treats upgrades as routine maintenance:
- quarterly review of pinned dependencies,
- scheduled upgrade windows,
- CI checks to prevent drift,
- clear policy on EOL dependencies.
This turns rare major bumps into manageable events rather than emergencies.
Align with broader platform modernization
InfoQ’s broader coverage across the ecosystem—from runtime updates like .NET previews, to infrastructure improvements like Cloudflare R2 latency reductions, to platform-level shifts like enterprise agent tooling—reflects a consistent theme: platforms evolve continuously.
Your application estate needs to be able to evolve continuously too. Dependency debt is one of the biggest friction points that prevents teams from taking advantage of:
- new runtime capabilities,
- improved security defaults,
- more efficient infrastructure options,
- and modern observability standards.
Conclusion: Let jQuery 4 be your forcing function—before the next mandate is
jQuery 4 arriving as the first major release in nearly a decade (and as a milestone in a ~20-year project history) is a reminder that “old and stable” doesn’t mean “low risk.” It often means the opposite: the dependency is so embedded that teams stop testing around it, stop inventorying it, and stop knowing what legacy behaviors they’re relying on.
Use this moment—whether or not you’re a heavy jQuery shop—to audit your stuck libraries, modernize your test safety net, and build an upgrade cadence. The goal isn’t to chase versions for their own sake; it’s to make future security fixes, platform upgrades, and modernization efforts predictable instead of painful.
Primary source: InfoQ, “jQuery Releases v4: First Major Version in Almost 10 Years” (https://www.infoq.com/news/2026/02/jquery-4-release/?utm_campaign=infoq_content&utm_source=infoq&utm_medium=feed&utm_term=global)