Replace a Silverlight app without pretending IE mode patched it

Support ended 12–13 October 2021. The installer is gone. There is no Microsoft converter. We will tell you whether to rewrite it as a desktop app, a website, or retire it.

Australian .NET team. We look at the app before anyone talks about a rebuild.

A leftover kiosk or IE mode is not a support contract. The work is a rewrite.

Still running Silverlight?

The app still opens on one locked-down kiosk. That is why it has been left alone.

Silverlight is a retired browser plugin. What is left in the wild is usually a line-of-business .xap, a media player, or an out-of-browser elevated-trust desktop that only launches on IE 11. Then the person who understood the XAML left, and “the kiosk still works” became the whole strategy.

You might recognise one of these:

  • The app only runs in Edge IE mode, or on a leftover IE 11 box
  • Isolated storage and plugin networking are tangled with the business rules
  • Smooth Streaming or DRM is the reason nobody has moved
  • Six people use it, so nobody wants to own a rewrite
  • The kiosk OS is also past its own support date
  • You are not sure whether to rewrite it or turn it off

You do not need a new brand, or a Blazor pitch. You need a clear read on the application you already have.

Why these apps stall

There is no current Silverlight. There is no Silverlight 6. Lines were Silverlight 3, 4, 5, and Silverlight for Windows Phone — all retired with the 2021 date.

Oct 2021

No installer

Unpatched plugin

Rewrite

Support ended 12–13 October 2021.

Microsoft’s 10 July 2019 announcement: end of support 12 October 2021. The Silverlight 5 lifecycle page: mainstream end 13 October 2021 06:59:59 AM PT. Last supported browsers at announcement were IE 10 (itself ended 31 January 2020) and IE 11. No Chrome, Firefox, or Mac support at that date. The installer is no longer available for download. There is no security servicing.

IE mode is a host, not a support contract.

The IE 11 desktop app on Windows 10 SAC ended 15 June 2022, and was permanently disabled via an Edge update on some Windows 10 versions on 14 February 2023. IE mode in Microsoft Edge is the remaining host, supported through at least 2029, with one year’s notice before retirement. Microsoft lists ActiveX — Java or Silverlight — among IE-mode capabilities, and immediately footnotes that Silverlight reached end of support on 12 October 2021. So IE mode can host the old plugin if it is still installed. It does not patch it.

There is no converter.

Microsoft did not ship a Silverlight to Blazor, WPF, or WinUI converter. The work is a rewrite of the XAML plus C# application against a supported UI stack, keeping any portable .NET logic that is not System.Windows or plugin-specific. Out-of-browser elevated-trust apps are still Silverlight. They are not a real desktop app. Leftover docs that point at XBAP are historical. XBAP is itself a legacy WPF-in-IE technology, not a 2026 destination.

The kiosk OS may be on the same clock.

Windows Server 2012 extended security updates end in mid-October 2026. A Silverlight app that “still works” on that box is two retired products stacked together. Media DRM and Smooth Streaming pieces have no 1:1 modern plugin. Domain logic tangled with XAML and isolated storage is why estimates slip.

None of that makes the business rules worthless. It does mean “IE mode supports Silverlight” is the wrong first sentence.

How we work

We start with the app, not with a destination.

1

Look at what you have

.xap or out-of-browser, what the app actually does, how much logic is portable C#, whether media DRM is involved, and which kiosk OS still hosts it. We will tell you what can be extracted, and what is a rewrite.

2

Decide the job

There are three honest outcomes. We recommend one, not all three.

3

Do the work in stages

Portable .NET logic comes across. Plugin networking, isolated storage, and XAML do not. Unused screens stay behind.

4

Hand it back so the next person can run it

Source, a short record of what changed, and an app someone else can understand — or a written decision to retire it.

Three honest outcomes

  • Rewrite as a Windows rich client — WPF or WinUI / WinAppSDK — if it must stay a desktop app.
  • Rewrite as a website — Blazor (server, WASM, or Hybrid) or ASP.NET Core MVC / Razor — if it should be a website. Hybrid here still needs a host; it is not a plugin.
  • Replace or retire — Power Platform or a packaged line-of-business product if it is mostly forms-over-data; retire it if usage does not justify a rewrite.

We will not tell you Microsoft still patches Silverlight. We will not tell you WordPress is the answer to a kiosk app. If you already know you want to keep the IE-mode kiosk until the OS dies, that is a decision — say it plainly. If you want an honest fork in the road, talk to us.

What we need for the first call

A screenshot or a kiosk URL, and a rough idea of what the app does, is enough to start.

  • In-browser .xap, out-of-browser elevated trust, or both
  • Which host still opens it (IE 11, Edge IE mode, a locked-down kiosk)
  • Whether media, DRM, or Smooth Streaming is load-bearing
  • How much logic might sit outside System.Windows
  • The Windows version under the kiosk
  • What “done” looks like: desktop rewrite, website, retire, or get a clear picture first

The first call is 30 minutes. You leave with a recommendation you can take to a manager, not a rewrite estimate pulled from thin air.

Related work

We have taken over and modernised ageing .NET systems for Australian organisations, including work with Data#3, Hastie, NESS, and NSW Health. That is related Microsoft web work, not a published Silverlight migration. Your app still starts with its own assessment. We will not pretend it is a project we have already published.

FAQ

Does IE mode mean Silverlight is still supported?
No. IE mode can host ActiveX such as Silverlight if the plugin is still installed. Microsoft’s own footnote keeps the end-of-support date at 12 October 2021. There is no security servicing.
Will Microsoft patch Silverlight if we stay on Server 2012?
No. The installer is gone. The plugin is retired. Server 2012 extended security updates end in October 2026 anyway. That patches the OS, not Silverlight.
Can you convert the XAML automatically?
No. There is no Microsoft converter to Blazor or WPF. Portable .NET logic can be extracted. The UI is a rewrite.
Is XBAP a supported way forward?
No. XBAP is a leftover WPF-in-IE technology. It is not a 2026 destination.
We only have the .xap and a kiosk.
That is common. Bring that.

Talk through the Silverlight app you already have

Thirty minutes. Bring a screenshot and a note of what the app does. We will tell you whether to rewrite it as desktop, rewrite it as a website, or retire it — and we will not call IE mode a patch.

Book a free 30-minute discovery call