Two apps, same name, very different engines. The new Outlook is a web based app in a window. Classic Outlook is the full desktop program offices have run for years. The differences that break daily work are specific - and they are listed here without hype.
Microsoft is moving everyone toward the new Outlook, but moving is not the same as upgrading. If your work depends on PST archives, add-ins, offline mail or shared mailboxes, the switch can quietly remove tools you use every day. This guide compares both apps on the points that actually decide office work, states honestly what the new app still cannot do, and ends with a simple verdict by desk type. Classic Outlook is still supported and there is no need to panic-switch - decide with facts, not with a toggle that appeared one morning.
Comparison panel with example wording - your build may show features in a slightly different stage.
The new Outlook is built on the Outlook web experience. It gives the same look on Windows, Mac and the browser, starts fast, and is free with Windows. Classic Outlook is the traditional desktop application that ships with Microsoft 365 and Office licences. It stores mail locally in OST and PST files, talks directly to Exchange, IMAP and POP servers, and carries twenty years of business features. Neither fact makes one app good and the other bad - but they explain every difference that follows. A web based app can only do what the web platform allows, and a desktop app can do far more with local files and other Windows programs.
Most comparison lists stop at colours and button positions. The breaks that matter are these. PST support in the new Outlook is limited and arriving in stages, so old archives are not fully at home there yet. COM add-ins and VBA macros do not run at all, because a web app has no COM. Offline work is a cache, not a full local mailbox. Mail for many account types is synchronised through Microsoft cloud services even for non Microsoft servers. And several deep settings - detailed rules actions, data file management, advanced account repair - are either simplified or missing. Everything else is taste.
Honesty needs both columns. The new app is cleaner, search is fast, it handles multiple Microsoft accounts gracefully, focused inbox and sweep tools are pleasant, and it receives new features first - including Copilot integrations. For a user whose mail is a single Microsoft 365 or Outlook.com mailbox, who works mostly online and keeps no local archives, the new app is honestly the simpler daily tool. It also ends the old problem of huge OST files corrupting on tired disks, because mail lives in the cloud mailbox and the local cache is disposable.
Classic remains the only choice when the job involves local data files, third party add-ins for billing or CRM, Send to OneNote style integrations, deep conditional formatting, client side rules that act on local folders, full offline work on trains and sites, or POP accounts managed the old way. It is also the app that the rest of this channel's Outlook guides assume - PST repair with ScanPST, archive discipline, registry limits - because those tools belong to the desktop world. Microsoft continues to support classic Outlook for Microsoft 365 customers, so staying is a legitimate decision, not stubbornness.
A home user on Outlook.com gains from switching today. A Microsoft 365 office worker with no add-ins can switch after a one week trial. An accounts desk, a PST archive keeper, an add-in dependent team or anyone working long hours offline should stay on classic and review later. That is the whole decision. The video walks through the differences on screen so you can see each one instead of trusting a feature list - watch it before you move a whole office, because the cost of switching back mid month is always paid in confusion, not in clicks.
See both Outlook apps side by side in the full video - every difference shown on a real PC, step by step.
Watch Full VideoThat is Microsoft direction over time, but classic Outlook remains supported for Microsoft 365 and Office customers and both apps can run side by side. Switch when the new app covers your features, not before.
Yes. They install separately and you can pin both. Your mailbox stays on the server, so testing the new app does not damage the classic setup.
It depends on the desk. Mail only users do well on the new app. Desks using PST files, add-ins, macros or heavy offline work should stay on classic Outlook for now.