Next.js 16 stretches the default image cache from 60 seconds to 4 hours, so a replaced CMS image can serve stale all afternoon
Next.js 15 leaves Maintenance LTS on 21 October 2026, ending its scheduled critical bug fixes and security patches. A dev.to upgrade guide lists Next.js 16 defaults that compile cleanly and still change what users see, including image caching and route-change scrolling.
The Engineer · Build desk
Timeline: Next.js 15 released 21 October 2024. On 21 October 2025 Next.js 16 became Active LTS and Next.js 15 entered maintenance. As of 13 October 2026 the latest stable release is 16.4.0 and the newest Next.js 15 backport is 15.5.27. Next.js 15 Maintenance LTS ends 21 October 2026.
| Date | Event | Claim |
|---|---|---|
| October 21, 2024 | Next.js 15 released | 1 |
| October 21, 2025 | Next.js 16 becomes Active LTS; Next.js 15 enters maintenance | 4 |
| October 13, 2026 | Latest stable: 16.4.0; newest Next.js 15 backport: 15.5.27 | 5 |
| October 21, 2026 | Next.js 15 Maintenance LTS ends | 1 |
What happened
- Next.js 15 has been in maintenance since 21 October 2025, the day Next.js 16 became Active LTS.
- Next.js 16 coerces image requests for any quality other than 75 to the nearest allowed value, so images can look different with no error in the build.
- A sitemap id is now a promise of a string, and plain JavaScript gives no warning when arithmetic on it returns the wrong number.
- Next.js 16 requires Node.js 20.9.0 or newer and TypeScript 5.1.0 or newer, and it drops older browsers.
Why it matters
- exposure After the cutoff, the next framework vulnerability gets its fix in Next.js 16 only. A Next.js 15 app upgrades under pressure or stays exposed.
- constraint The policy allows a patch for an unsupported version only in rare circumstances for severe issues. A Next.js 15 team cannot plan around that.
- cost Teams that used next build as their lint gate now ship lint errors unless they add a separate lint step to CI.
- decision The Node.js version in hosting, the Node.js image in CI and Dockerfiles, and any older-browser promise to clients all need settling before the upgrade starts.
A passing next build proves the code compiles under the new rules [18]. The guide points to the official upgrade guide's own migration checklist for the same limit: a green build alone does not close runtime findings [13].
The image cache change is the one with a number. Optimised images without cache headers now stay cached for four hours instead of sixty seconds [7]. That is 240 times longer [21]. The guide's example is an image replaced in a CMS that keeps serving the old version all afternoon [8].
The wording covers only images without cache headers, so the exposure depends on what your image sources send. The check is also slow. A staging test that swaps an image has to wait up to four hours for the old copy to expire. We would start it first for that reason.
Image quality is a visual check. The guide's summary says quality now defaults to 75 only [19]. Components that pass another value are the ones to compare against screenshots from the old build.
Two more changes show up only in use. During route changes, Next.js now leaves a global scroll-behavior: smooth in place, so a navigation that once jumped straight to the top scrolls there with an animation [10]. And proxy.ts runs on Node.js only [12]. The summary lists the second without detail, so any code in that file that assumed another runtime needs a run under Node.js before release.
The guide's order is the upgrade codemod, then the separate next-async-request-api codemod, then the tests a build cannot run [17]. It describes itself as a checklist its authors work through on every Next.js upgrade [20]. It does not include measurements from any app, so how hard each default bites depends on your image sources, your CI and your CSS.
Maintenance LTS gives a major version only critical bug fixes and essential security updates, for two years from its original release [3]. Next.js 15 shipped on 21 October 2024, so the window closes on 21 October 2026 [1]. The guide's version numbers are current as of 13 October, eight days before the cutoff [22]. On that date the latest stable release was 16.4.0 and the newest Next.js 15 backport was 15.5.27 [5].
What to watch
- A Next.js 15 release newer than 15.5.27 after 21 October would show how the rare-circumstances exception is applied.
- The first framework security advisory after the cutoff, and whether its fix lands in Next.js 16 only.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence50
- Adoption
- Insufficient
- Hype gap+8
- Incentives
- Insufficient
- Confidence55
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
Next.js 15 reaches the end of its Maintenance LTS period on 21 October 2026, two years after its release on 21 October 2024.
- [2]
The Next.js support policy allows patching unsupported versions "in rare circumstances" for severe issues, which the guide calls an exception, not a plan.
- [3]
In Maintenance LTS a major version receives only critical bug fixes and essential security updates, for two years from its original release date.
- [4]
Next.js 16 has been Active LTS since 21 October 2025, and Next.js 15 has been in maintenance since the same day.
- [5]
As of 13 October 2026, Next.js 16.4.0 is the latest stable release and the newest Next.js 15 backport is 15.5.27.
- [6]
Image requests for a quality other than 75 are now coerced to the nearest allowed value, so images can look different without any error in the build.
- [7]
Optimised images without cache headers now stay cached for four hours instead of sixty seconds.
- [8]
Per the guide, an image replaced in a CMS can keep serving the old version all afternoon under the four-hour default.
- [9]
next build no longer runs ESLint, so a pipeline that relied on the build to catch lint errors now ships them.
- [10]
Next.js no longer overrides a global scroll-behavior: smooth during route changes, so navigations that used to jump to the top now animate.
- [11]
A sitemap id is now a promise of a string, and plain JavaScript will not warn when arithmetic on it produces the wrong number.
- [12]
proxy.ts runs on Node.js only.
- [13]
The guide says the official Next.js upgrade guide states in its own migration checklist that a green build alone does not close runtime findings.
- [14]
Next.js 16 requires Node.js 20.9.0 or newer and TypeScript 5.1.0 or newer, and drops support for older browsers.
- [15]
The guide says three places tend to get missed: the Node.js version in hosting configuration, the Node.js image in the CI workflow and any Dockerfile, and the browser support promise to clients.
- [16]
According to the guide, the next vulnerability disclosed in the framework will be fixed in Next.js 16, and a Next.js 15 app will either need the upgrade done under pressure or stay exposed.
- [17]
The guide says to run the upgrade codemod and the separate next-async-request-api codemod, then test the things a build cannot.
- [18]
A passing next build proves the code compiles under the new rules.
- [19]
The guide's summary says image quality now defaults to 75 only.
- [20]
The guide describes itself as the checklist its authors work through on every Next.js upgrade.
- [21]
The new image cache default is 240 times the old one.
- [22]
The guide's version-check date of 13 October 2026 falls eight days before the 21 October 2026 cutoff.
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Sources
1 independent publisher whose own reporting we read for this story.
- dev.toNext.js 15 Support Ends Oct 21: The Upgrade Changes Your Build Won't Catch
1 article · October 14, 2026
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