Microsoft is building a new Outlook app for Windows and Mac powered by the web

Outlook Web App
Outlook Web App (Image credit: Windows Central)

What you need to know

  • Microsoft is building a new Outlook client powered by the web.
  • The project is codenamed Monarch.
  • The effort is part of Microsoft's "One Outlook" vision detailed last year.

Microsoft is building a universal Outlook client for Windows and Mac that will also replace the default Mail & Calendar apps on Windows 10 when ready. This new client is codenamed Monarch and is based on the already available Outlook Web app available in a browser today.

Project Monarch is the end-goal for Microsoft's "One Outlook" vision (opens in new tab), which aims to build a single Outlook client that works across PC, Mac, and the Web. Right now, Microsoft has a number of different Outlook clients for desktop, including Outlook Web, Outlook (Win32) for Windows, Outlook for Mac, and Mail & Calendar on Windows 10.

Microsoft wants to replace the existing desktop clients with one app built with web technologies. The project will deliver Outlook as a single product, with the same user experience and codebase whether that be on Windows or Mac. It'll also have a much smaller footprint and be accessible to all users whether they're free Outlook consumers or commercial business customers.

I'm told the app will feature native OS integrations with support for things like offline storage, share targets, notifications, and more. I understand that it's one of Microsoft's goals to make the new Monarch client feel as native to the OS as possible while remaining universal across platforms by basing the app on the Outlook website.

Over a year away

One Outlook Thumb

Source: Microsoft (Image credit: Source: Microsoft)

Microsoft will begin to preview its new Monarch client towards the end of this year, with plans to replace the Mail & Calendar apps on Windows 10 sometime in 2022. Microsoft also wants to replace the legacy Win32 Outlook client, but that is a goal which appears to be much further out and will be a gradual process as the legacy client is a mammoth that is not easily replaced.

Those curious about how this experience will look and feel can install the Outlook Web app via your web browser today. Of course, that won't provide you with all the integrations Microsoft has planned for the Monarch client, but it does give a general idea of the kind of experiences you can expect to have when using it.

The Mail & Calendar apps on Windows 10 are in maintenance mode between now and when the Monarch client is ready to replace them. I'm told that the existing apps will get a minor UI update later this year to bring them in-line with other UI updates going on with Windows 10's big Sun Valley update, but the apps themselves will eventually be replaced by Monarch.

It's worth noting that these plans are still over a year away from coming into effect, so things may change between now and then. In the meantime, what are your thoughts on Monarch? Let us know in the comments.

Zac Bowden
Senior Editor

Zac Bowden is a Senior Editor at Windows Central. Bringing you exclusive coverage into the world of Windows 10 on PCs, tablets, phones, and more. Also an avid collector of rare Microsoft prototype devices! Keep in touch on Twitter: @zacbowden.

  • Does it still remain native for Mac ARM this way?
  • Of course. Why wouldn't it? By then there'll be no Intel Macs being produced.
  • This article smells like an Electron application all over. Not that I'm opposed to it, Microsoft's VS Code is a prime example of Electron done right – Teams on the other hand, not so much.
  • I believe the Monarch client uses WebView2 on Windows.
  • That would be cool.
  • That would be much better. Better if they do it as a proper PWA and not bloated mess like most Electron apps. VS Code got this right, though IMO it could be bit faster. But Microsoft Teams despite its great feature set, it is such a hog which is quite unacceptable on corporate machines where many hardware won't be the latest and the greatest, and you have to run teams on the background sucking some resources. I hope they at least make the title bar not visible like on current Mail and Calendar app. Making the UI footprint more leaner and eleminate uncessary blank unused space.
  • Yeah Teams has been a headache for IT's.
  • I've been wondering what Microsoft intends to use for Monarch. It sounds like a PWA to me.
  • A powerful PWA it seems like.
  • Not a fact but I kinda feel like they might try and flex some react-native desktop on this one.
  • So a PWA app?
  • The site ( appears to be built with Blazor 3.2.0, Microsoft's .NET based framework for creating WebAssembly apps. The look and feel hasn't even been changed yet from what you get when you create a new empty Blazor app.
  • Pretty sure that's not an official site. Anyone can (I mean, has to) claim an unique URL when deploying a web app to Azure.
  • So just another bloated web app? Microsoft forgot how to make software.
  • "It'll also have a much smaller footprint" Troll better.
  • Highly doubt, its only another webview app.
  • You don't even know what you are talking about.
  • The one and only reason to ever make an application with "web" technologies is to gain cross-platform capabilities. That's because such an application is much, much, much more difficult to create and is similarly much less efficient and functional. Perhaps one day it will dawn on the anything-but-Windows crowd that the technology that makes web software cross-platform NEED NOT HAVE TO RUN IN A BROWSER! And more, IT NEED NOT USE SPAGHETTI SCRIPT LANGUAGES!
  • Oh how I hate this "... so things may change between now and then." it's always 80% more chance to happen
  • Long overdue! They need to support multiple accounts (email, calendar, and storage) from various providers (MS, Google, Apple, AOL, etc.) and have the view all accounts option they have in Android Outlook app.
  • I've long suspected Google Workspace isn't supported in the Outlook Desktop apps as it would take business away from Exchange. Although the Windows 10 apps do natively support the providers you mention.
  • 'and is based on the already available Outlook Web app' Are we talking about 'Cause that is godawful, and severely lacking in features, when you finally get by the seconds long delay of every single action.
  • It only says "based" on.
  • I'm going to miss transparency and good design.
  • As long as they don't try to pull a OneNote again and replace my Office Outlook with this casual-consumer-grade thing...
  • This. Always my concern with this app-like approach to all things now. Sometimes, you need really heavyweight programs, not some toy clients. Hope they don't water down outlook and make it an 'app'.
  • The Microsoft Store version of OneNote is very powerful now, and also very fast and stable. It also has much better synching across platforms (accompanied by much better mobile versions). You should try it. I used to hate it but I've since switched from the 2016 desktop version.
  • Yeah, OneNote UWP is actually one of the few Microsoft apps that showcase what UWP app should be. It is well made and pretty much the same feature with Desktop client. So I was kinda confused why they shift focus back to desktop client when their UWP is as good if not better. Sure some things like 3rd-party integration may be missing, but those should be solvable ones as they continue to improve it. But alas, they decided to abandoned UWP version instead and go back to the bloated desktop client. I still use the UWP because it is as good and way faster than the old desktop client. Sadly with new WIndows Ink Workspace, they even remove OneNote integration and quick launch feature from the lockscreen.
  • They haven't abandoned the OneNote UWP. Why do you say that? It's the main version of OneNote now.
  • The syncing engine has been moved to Office OneNote too, so that's not an advantage any more. They did that as part of Desktop version's resurrection. I really dislike the single-line ribbon, it almost defeats the purpose of a ribbon (I always enable full ribbon on web apps, but UWP OneNote has no such option... nor features to populate it with lol). UWP OneNote lacks offline notes, which is very important in the enterprise sector, it lacks customisable title bar, which is part of every office app (even Mac OneNote has that, come on!) The amount of settings on UWP is laughable. The customisation of the whole UI is better on Office Onenote, I can move all the navigation panes all over the place. It supports Addins and has better Office integration (naturally). I have tried UWP OneNote, as have many others. As far as UWP apps go, it's decent, but compared to a proper Office OneNote it is still inferior. This is why enterprise and people like me did not allow Microsoft to kill Proper OneNote with this inferior version. It is now called THE "OneNote", so it must be here to stay. They better not try this again with Office Outlook. If it's limited to the UWP Mail app, then they can do whatever they want with it, I don't care much.
  • Everything you mentioned here is not needed a make a note. In terms of usability UWP OneNote is the best choice for all students and average consumers
  • OneNote doesn't exist to make small text or handwritten notes. It exists to organize large collections of notes. The UWP app completely was nerfed to the point that it was more on par with Apple Notes or Samsung Notes than Office OneNote itself. For many of the people who use OneNote, it was not a usable app. It was far too pared down, and Microsoft are not agile enough to develop software fast enough to catch it up. They haven't been that agile since the Mid-90s. Apple is the only platform developer agile enough to release unreleased software and finish things off before the next major update hits (i.e. macOS Yosemite was such an instance of this happening). If Microsoft launches something half-baked, it's likely to remain that way for the next 3-4 years; before they decide they want to try something else "all new" and start reinventing the wheel again.
  • UI preferences aside, I really don't get what you are talking about. UWP OneNote works fine offline - it's just that you can't save local backups anymore. Synching greatly improved with the UWP first - I know because during that time I was using both. I don't use or need any addins. Sticky Notes are soon to be fully integrated. I am a heavy user - I got through grad school with OneNote and I teach with it - and I'll take the UWP over the desktop version hands down.
  • It's not about "working offline", it's about sensitive data not being uploaded to Microsoft servers. This may be irrelevant for you shopping lists, but quire relevant for the Enterprise. You all keep disagreeing with me (What a shock on this site), but Microsoft would not have resurrected an "unwanted" product and then renamed both version to make the Win32 one The "OneNote" for me alone. Sticky notes are integrated into the Desktop version already lol.
  • OneNote UWP is great. I switched over completely a few years and I use it daily.
  • How do these web based apps work when your device is offline? I very frequently use my devices when they have no internet connection. Do these types of apps require a persistent connection to function?
  • Nope, they can work offline without issues, once installed the website's files and data is cached locally.
  • Imagine all the fun Microsoft will have abandoning or canceling this. Or releasing it half baked and then letting it rot and decompose, like Groove for example.
  • MS is going to do that to an Office product? Really?
  • Are you going to say that for every single thing Microsoft works on? Not sure why people like you keep rehashing old things. Some things work and gain traction, some things don't and they get shelved. Doesn't matter if you're apple, Google, or Microsoft.
  • We're talking about flagship Office product here; this is outlook that we're talking about not Planner or Task. It's outlook dude.
  • Really? I wished they had thought and worked on it sooner rather than later.
  • Yes, way overdue. The Win 10 Mail app is just an embarrassment.
  • How so? I use it all the time and it's fine as a basic email/calendar app. On my desktop I personally use the win32 outlook app because I like how it looks and functions, but when I'm on the go or on my surface another laptop I just use the mail and calendar app and it works fine.
  • I think it's great. I stopped using Outlook and Thunderbird long ago. Institutional accounts and everything. Don't need all the power.
  • I'm really glad to see this and just bummed it will take this long, but I guess the integrations will take a while. Outlook on the web has way more features than the Mail and Calendar app (which feels like abandomware with pretty broken Focused Inbox for Gmail accounts, no add-ins, no tabs, pretty bad search, no pinned emails, etc.) I just hope it will feel native, get a touch of fluent design, and of course be able to handle non-Outlook accounts.
  • I am glad they are not in a hurry to rush out a successor to the Win32 Outlook client. I know it's an 800-pound gorilla but most of our lives in the business world revolve around it. They do NOT want to screw that one up.
  • It will be take a while before the legacy Outlook desktop client to get replaced by new one. But they have to start now making a future replacement for it. Outlook is indeed an essential tool in the business, but gosh it is already been a bloated mess, IT would love to get a new ones that have less issues, better leaner features and faster to use, which will reduce user's helpdesk complaints in the long run. Transition can be rough thoguh if there is a new UI to be introduced, but I doubt we will get a massive UX shift like what was before from old toolbar UI to Ribbon UI.
  • Not interested in "web apps". The native app will always be better.
  • Eh never speak in absolutes
  • I agree. As a long time user of MS Office programs I have found the move to internet based systems to be very frustrating. One significant issue is features available on the desktop versions of apps are simply not available on the web versions. MS XL is particularly bad for this, especially for accountants, who presumable are major users of the program. As for Outlook online... It's just not very nice is it? If I had to say which version was the improved, futuristic version of the other I would say the Outlook desktop program is light years ahead of Outlook online. On that topic, why is this news? I can already use Outlook online on any kind of computer I want, I just need a web browser. Since Outlook for a Mac is terrible I use the online version on my Mac and the desktop version on my PC. If ever a program didn't need improving it's MS Outlook. It absolutely does what I want it to do perfectly. The online versions simply sacrifice good features, like the UI, for web compatibility. It's a waste of time, they don't work properly, suffer significant lag over desktop versions (despite my 1000GB fiber connection), and they are no fun to use at all. I wish Microsoft would ask us what we actually want before forcing an unwelcome 'update' on us. :-)
  • Funny how this is web based, yet doesnt target Linux.
  • Usage issue, 80% of Linux user owns a Mac or Windows.
  • Wow long time overdue. The Windows 10 UWP apps are pointless. The Win32 apps are way to legacy.
  • Maybe this also means we’ll finally get the ability to switch between Microsoft accounts on the web version like you can so easily with google accounts.
  • The Outlook (for Business/O365) website lets you open another user's email in the same tenant. Click your Profile photo in the top right, then click Open Another Mailbox.
    Once you have the URL for that mailbox, you can go there directly using a shortcut as well.