Knockout.js End of Life (EOL) Dates & Support Timeline
Complete end-of-life dates, support windows, and security status for all Knockout.js versions. Data sourced from endoflife.date and official vendor documentation. Updated at every deploy.
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[](https://endoflife.ai/knockout)
Knockout.js lifecycle status — the real story
Knockout.js was a pioneering MVVM framework of the early 2010s, and it occupies an unusual lifecycle position: not formally end-of-life, but functionally finished. The 3.5 line released in February 2019 remains the only maintained branch, receiving rare compatibility patches (3.5.3 arrived in March 2026) with no feature development for years.
Roughly 110,000 weekly npm downloads and a long tail of enterprise line-of-business apps — especially older ASP.NET applications where Knockout shipped in the default templates — keep it in production far beyond its ecosystem's lifespan. Versions before 3.5 should be treated as unsupported.
The practical risk is less about Knockout CVEs and more about ecosystem decay: modern build tooling, TypeScript typings, and security tooling increasingly assume frameworks Knockout predates, which raises the cost of every year of deferral.
Knockout.js release and support pattern
Across the 3 release lines with a published release date, Knockout.js has shipped a new line roughly every 2.7 years (median interval). A line typically stays supported for about 2.7 years from its release to its end-of-life date (measured on the 2 lines with both dates published).
Of the 3 release lines tracked, 2 are past end of life and 1 is still within support. The newest line, 3.5, was released February 21, 2019. No end-of-life date is currently published for the 1 supported line.
Computed from the tracked release data at every build — the figures above are the dates in the table, restated, not an editorial estimate.
What does Knockout.js end of life mean for your organization?
When a version of Knockout.js reaches end of life, the maintainers stop issuing security patches. Vulnerabilities discovered after this date are publicly disclosed on the National Vulnerability Database, exploit code appears on GitHub, and your systems remain permanently exposed.
The CVE blind spot: Most vulnerability scanners check for known CVEs but do not flag the accumulation of unpatched vulnerabilities in EOL software. With a zero-day, nobody knows about the vulnerability. With EOL software, the vulnerability is public — listed, rated, and often weaponized — but no patch will ever exist. This is the most dangerous gap in enterprise security posture.
Organizations running EOL Knockout.js should treat it as a vulnerability class in their risk register, apply compensating controls (network segmentation, enhanced monitoring, access restriction), and prioritize migration to a supported version.
Your options when Knockout.js reaches end of life
There are four realistic paths. Which one is right depends far more on how long the system needs to keep running than on the version you are on today.
| Option | Best when | Watch out for |
|---|---|---|
| Move to a supported version | The system will outlive the current version's support window and you can schedule the work | Budget for compatibility testing, not just the upgrade itself — that is where the real cost sits |
| Replace the component | The project is unmaintained, or a better-supported alternative exists | The replacement has its own lifecycle and its own end-of-life date — you are changing vendors, not escaping the problem |
| Buy extended support | Migration is genuinely underway but cannot finish before the deadline, or the workload is frozen by certification or a third-party application | A bridge, not a destination — every year purchased is a year the migration still has to happen |
| Document accepted risk | The system is isolated, short-lived, or scheduled for retirement | Only defensible with real compensating controls and a written decision — auditors treat undocumented end-of-life software as a finding |
How to choose, in one question: how many more years does this system need to run? Under a year, extended support (where it exists) is usually cheaper than an emergency migration. One to three years, migrate — support purchased repeatedly costs more than doing the project once, and the project only gets harder as the version ages. Indefinitely, migrate now and plan the next migration before it surprises you.
Worth saying plainly, because vendors selling extended support rarely will: extended support is often the more expensive choice over a multi-year horizon. It is the right answer when a deadline is genuinely unreachable, not as a default. Compare the annual fee against the one-time cost of migrating before committing to either.
Formalizing decisions like this across your estate? Our free EOL policy template is a ready-to-adopt policy with risk tiers, remediation SLAs, and audit mapping — no signup, free to use and share.
Extended Support Options
If you cannot migrate immediately, extended support vendors provide continued security patches for EOL Knockout.js versions. This is a bridge, not a permanent solution — plan your migration in parallel.
Knockout.js has 2 versions past end of life — security patches have stopped, but CVE disclosures haven't. The good news: extended support for Knockout.js exists — vetted vendors ship security patches for years past the official date. Right now that coverage spans Knockout.js 3.5.1, 3.4.2, 2.3.0. Tell us where to reach you and we'll reply with matched options and pricing guidance — or an honest "no vendor covers this."