Historically, worries about app compatibility have helped to make upgrading to a new version of Windows such a major undertaking that many organisations skipped alternate releases.

Microsoft’s FastTrack App Assure programme has been running for over two years, backing up the promise of app compatibility in Windows 10 with development support, and even changes in Windows when that’s what it takes to get an application working. Extending that from Windows 10 and Office 365 to Edge, Windows Virtual Desktop and now Windows on Arm is Microsoft’s way of helping organisations feel comfortable stepping onto the ‘as a service’ treadmill, where new features are continually arriving and getting rolled out, with no more ‘big bang’ migrations.

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“When we launched the programme, it was really intended to alleviate those fears, and help customers understand that their experience moving to Windows 10 and Office 365 is going to be very different from moving to Windows 7 and earlier versions of Office, and that even if their critical apps experienced any issues, we’d be there to help them,” Aleks Lopez, principal program manager for App Assure, told TechRepublic.

Two years on, the number of true compatibility issues has been extremely low, but the ability to reassure customers that they wouldn’t have problems — and fix the few issues that did crop up — has helped large numbers of organisations adopt new software, Lopez said.

“When we look at the number of apps evaluated through customers, we’ve seen over 700,000 applications — the exact number is 709,895. Of those, only 1,822 were broken. And when you take a look at the number of actual applications that experienced compatibility issues relative to the entire app estates of the customer, that represents just a 0.25% app failure rate. That means that over 99% of applications are compatible. The goal is, through customer feedback and engineering, to take that 0.25% and continually chip away at it to be smaller and smaller and smaller.”

That includes keeping compatibility in newer releases of Windows 10. “Once a customer is on Windows 10, when they’re taking updates, we don’t want them running into the same issue that they’ve experienced before,” Lopez said.

Configuration not bugs

The few true compatibility problems are rarely down to Windows, and the most common issues aren’t actually compatibility problems but not using the latest version of software or not having the right configuration.

“There’s a configuration change they may not have been aware of, or a setting they could have set: we show them how to set that and configure that and they’re up and running. Or they may not be aware that their ISV has created a free upgrade or a paid upgrade of an application, and we help point them to that,” Lopez explained.

The next most common issue is line-of-business apps, written by organizations, that need more work (think elderly .NET or web applications). “They might be relying on a deprecated feature of Windows, and so what we do is help them code around that and upgrade their application.”

Next is ISVs needing help to make their applications work on Windows 10, and after that is changes in the customer’s own environment: “They’re strengthening their security posture, which naturally will break those 1990s apps, so we help them work through those, changing GPO settings or network stuff.”

Bugs in Windows are the rarest cause, Lopez said: “I can’t even tell you the percentage — it’s a teeny, tiny sliver of the overall.”

The same has been true with Chromium-based Edge compatibility questions. “We didn’t quite know what to expect, but we thought we’d have pretty high compat rates because of the native Chromium engine and the IE mode support,” Lopez said. “What’s happened is the majority of the escalations we’re actually getting aren’t compat issues, they’re help and how-to questions. Customers are not configuring their site list modes correctly, so the IE mode isn’t kicking in to run their legacy sites.”

Getting help from Microsoft means reassurance for customers. “We hear the relief in their voices when someone’s actually on the phone saying ‘we’re gonna hang on with you, and we’re gonna figure this out’,” says Lopez, who notes that there are concrete cost savings too.

“There’s a level of expertise they’re getting when they’re working with engineers who have access to source code inside Microsoft. And so, when we do remediate something, it’s often much faster than a customer could remediate on their own, because of the knowledge we have of our own products, but then also the breadth of different issues that we see. So we can quickly rule out things that it likely isn’t, and then also quickly zero-in on a root cause faster than a customer can on their own.”

Microsoft asks organizations how many users are affected by the issues they report and how many users upgrade to Windows 10 after the issue is solved. “We’ve unblocked 77 million devices, and when we fix something for a customer, that end user is not calling into support. We’ve prevented 42 million helpdesk escalations, which has saved customers $7.4 billion,” Lopez claims.

That’s on top of how much organizations have saved who might otherwise have been paying for extended support agreements while they tested and rewrote applications, or the cost of security or data breaches they might have suffered by staying on an earlier version of Windows, when Windows 10 doesn’t have the same vulnerability.

The numbers may be large, but Lopez points out that the organizations using App Assure don’t have to be, says Lopez. “We’ve worked with customers as small as where the one person at a company that runs the office is the de facto IT manager, and also happens to do their social media.”

Platform commitment

Given how often Microsoft has said that Windows on Arm is ‘just Windows’, extending App Assure to cover it is a logical, but important, progression, along with the x64 emulation that will come to Windows Insider builds on Arm in November, and the launch of the updated Surface Pro X. (Microsoft also had a strong presence at the recent Arm DevSummit, talking about Arm and Windows on PC, IoT and server workloads.)

The Windows on Arm team has done a lot of work on app compatibility, from extra settings to tweak to get individual apps to work (which may be required for things like software that checks for a valid licence) to writing shims that include those settings even for some fairly obscure utilities. In our tests, we’ve found that business desktop software like CorelDRAW has run without issues and with reasonable performance. Adding Windows on Arm to App Assure goes a step further and gives the platform a vote of confidence — not just that Windows software will work, but also that Microsoft is actually committed to Windows on Arm for the long term

“We see the market opportunity for Arm, we’re seeing an increased demand for Arm devices, and so we are very happy to extend that scope — especially since, traditionally, app compat has been the biggest hesitation for enterprise customers to adopt devices,” Lopez told TechRepublic.

The support covers not just Microsoft’s Surface Pro X models, but all Windows on Arm OEM devices. To start with, it’s for 32-bit x86 apps. “What’s in scope for the service is x86 32-bit customer-developed line-of-business apps, x86 32-bit third-party vendor apps and add-ins with drivers that operate in kernel mode, x86 32-bit Microsoft first-party apps and, of course, web apps and PWAs,” Lopez said.

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64-bit apps and add-ins aren’t covered, although that’s expected to change once 64-bit emulation is released (perhaps in Windows 10 21H1). Also not in scope, Lopez said, are 16-bit apps and add-ins, and apps that rely on frameworks that aren’t available on Windows on Arm: “applications dependent on OpenGL such as AutoCAD and OpenCL such as Photoshop.”

Drivers may also be an issue for compatibility, Lopez cautioned. “The challenge that we’re seeing is, what do you do with applications that have kernel level drivers? That’s very difficult and you can’t just work around that. But there hasn’t been anything that’s been a super-big blocker that we haven’t been able to get around with our customers.”

The Windows on Arm support has been in a private preview and, as with the Windows 10 App Assure requests, it’s not just customers who are asking Microsoft for help, Lopez noted. “In the Arm space, the biggest thing we’re seeing is the app readiness. So third-party vendors are coming to us saying, ‘okay, we now see the value and the potential in this platform, and we want to port over our applications to be compatible on Windows 10 on Arm’, so we’re helping them there.” Hopefully that demand will also see applications being recompiled natively for the platform in future.

Supporting Windows on Arm through App Assure also sends a message not only to the third-party software developers who haven’t already started work to take the platform seriously, but also to product teams at Microsoft who haven’t necessarily prioritised Arm support.

Sometimes that’s because a development library or framework hasn’t been available. Porting all the dependencies takes time, and full ARM64 support only comes with .Net 5 later this year. However, Electron, node.js, Chromium V8 and the Chromium Embedded Format (CEF is used by Spotify amongst others) are now available for ARM64. Sometimes it’s a product team not having enough resources for something they may not have seen as a priority.