The short answer: O365 vs M365 are not the same thing, even though the terms are frequently used interchangeably. Microsoft has been consolidating its cloud productivity and business services under the Microsoft 365 brand — understanding O365 vs M365 helps clarify differences in products, features, and pricing between the original Office 365 and the new Microsoft 365.
For business decision-makers evaluating subscriptions or renewing contracts, knowing the O365 vs M365 distinction matters to understand what they are actually paying for.
Overview
Office 365 (O365) was the original brand for Microsoft’s cloud subscription service — primarily focused on Office applications (Word, Excel, PowerPoint) and cloud services (Exchange Online, SharePoint, Teams). Microsoft 365 (M365) is an expanded brand that includes everything in Office 365 plus additional security, device management, and compliance capabilities — depending on the specific plan. Microsoft has progressively rebranded most Office 365 plans as Microsoft 365 plans, but the specific capabilities included vary by plan tier.
- “Office 365” is Microsoft’s older branding; most plans have been renamed under “Microsoft 365”
- Microsoft 365 plans at higher tiers include security, device management, and compliance tools not in the original O365 plans
- The core Office applications and cloud services (Exchange, SharePoint, Teams, OneDrive) are included in both
- A major part of the O365 vs M365 comparison lies in the additional security and management features included in Microsoft 365 plans
- Most business customers have already transitioned from O365 to Microsoft 365, making the O365 vs M365 discussion important for licensing and security planning
The 5 Why’s
- Why did Microsoft rebrand Office 365 to Microsoft 365? The rebrand reflects Microsoft’s strategy to position its cloud productivity suite as a comprehensive business platform rather than just an Office application subscription. Microsoft 365 packages productivity (Office apps), communication (Teams, Exchange), security (Defender, Intune), and compliance features together — a broader value proposition than “Office in the cloud.”
- Why does the specific plan tier matter more than the brand name? Whether a plan says “Office 365” or “Microsoft 365” matters less than which features are included in the specific plan. A Microsoft 365 Business Basic is missing features that an Office 365 E3 included. Comparing plans requires looking at the specific feature list, not just the brand name.
- Why do Microsoft 365 Business Premium and Microsoft 365 E5 represent a meaningfully different product than basic Office 365 plans? Higher-tier Microsoft 365 plans include Microsoft Defender for Business or Defender for Endpoint (endpoint security), Microsoft Intune (device management), Azure AD Premium (advanced identity features like conditional access and Privileged Identity Management), and Microsoft Purview (compliance and information protection). These are substantive additions beyond productivity applications that fundamentally improve security posture.
- Why do organizations frequently not know which plan they are on or what it includes? Microsoft 365 plans have been renamed, restructured, and rebranded multiple times. Organizations that purchased Office 365 several years ago may be on plans that have been discontinued or renamed. License assignments within organizations are frequently not reviewed against current needs. IT staff changes mean institutional knowledge about why specific licenses were chosen may be lost.
- Why is the Microsoft 365 Business Premium plan specifically the standard recommendation for SMBs from a security standpoint? Microsoft 365 Business Premium includes Microsoft Defender for Business (endpoint detection and response), Intune (mobile device and application management), and Azure AD Premium P1 (conditional access). For SMBs without dedicated security staff, this combination provides enterprise-grade security tooling at a price point and management level accessible to smaller IT teams. Security guidance from Microsoft and most MSPs consistently recommends Business Premium for SMBs handling sensitive data.
What Changed: O365 to Microsoft 365 Branding
| Old Plan Name | New Plan Name | Core Change |
|---|---|---|
| Office 365 Business Essentials | Microsoft 365 Business Basic | Name change; similar features |
| Office 365 Business Premium | Microsoft 365 Business Standard | Name change; similar features |
| Microsoft 365 Business (bundled) | Microsoft 365 Business Premium | Clarified bundling of security features |
| Office 365 E1 | Microsoft 365 E1 | Name change; similar features |
| Office 365 E3 | Microsoft 365 E3 | Added compliance features |
| Office 365 E5 | Microsoft 365 E5 | Added security and compliance features |
What Microsoft 365 Adds Over Basic Office 365
The meaningful additions in Microsoft 365 plans (particularly Business Premium and above) compared to earlier Office 365 plans:
Security:
- Microsoft Defender for Business / Defender for Endpoint: endpoint threat detection, investigation, and response
- Microsoft Defender for Office 365: advanced email threat protection against phishing and malicious links
- Azure Information Protection: data classification and protection
Device Management:
- Microsoft Intune: mobile device management (MDM) and mobile application management (MAM)
- Windows Autopilot: automated device provisioning and enrollment
Identity:
- Azure AD Premium P1: conditional access, self-service password reset, Azure AD Join
- Azure AD Premium P2 (E5): Privileged Identity Management, Identity Protection
Compliance:
- Microsoft Purview: data governance, compliance management, eDiscovery, audit
What Stays the Same
Regardless of whether you are looking at an “Office 365” or “Microsoft 365” plan, the core productivity components are consistent:
- Word, Excel, PowerPoint, Outlook (desktop apps in Standard and above plans)
- Exchange Online for business email
- SharePoint Online for document management and intranet
- Microsoft Teams for communication and collaboration
- OneDrive for Business for personal cloud file storage
Final Takeaway
The O365 vs Microsoft 365 distinction is primarily a branding evolution, but the capability differences between plan tiers are substantive — particularly around security and device management. Organizations reviewing their licensing should look at what their current plan actually includes and compare that to what their security requirements demand, rather than assuming that “Microsoft 365” in the plan name means they have the security features their environment needs.
Frequently Asked Questions
What is the difference between O365 and M365?
Office 365 is the productivity suite: Word, Excel, Outlook, Exchange, SharePoint, and OneDrive. Microsoft 365 is a superset that bundles those same applications with Windows Enterprise, Intune device management, and Entra ID identity security. Both brands are still sold today, so the plan tier matters more than the name.
The two are not competing products and Microsoft 365 is not simply the new name for Office 365. For small and medium business plans the rebrand was mostly cosmetic. For enterprise plans the two names describe genuinely different scopes of product, sold side by side at different prices. That distinction is where most renewal confusion originates.
Is Office 365 E3 the same as Microsoft 365 E3?
No. They are separate products still sold alongside each other. Office 365 E3 covers the applications and cloud services. Microsoft 365 E3 bundles that same Office 365 E3 with Windows Enterprise, Microsoft Intune, and Entra ID P1, so it costs roughly a third more.
The same relationship holds at the E5 tier. This is the most consequential misunderstanding in Microsoft licensing, because an organization can believe it has device management and identity protection when its plan includes neither. As of the July 2026 packaging update, Microsoft 365 E3 also includes Defender for Office 365 Plan 1, Intune Remote Help, and Intune Advanced Analytics, so the gap between the two lines widened rather than narrowed.
Does Microsoft 365 include Teams?
It depends on the SKU. Microsoft unbundled Teams from enterprise suites in 2024, then restored the with-Teams versions worldwide in November 2025. Both variants are still sold, so a plan may or may not include Teams. Check whether your SKU name says no Teams.
The unbundling followed a European Commission antitrust investigation, first applied to the EEA and Switzerland in October 2023 and extended globally in April 2024. Existing customers generally kept Teams in their current SKUs and renewals. The practical implication for a licensing review is that Teams entitlement can no longer be assumed from the plan family alone, and the cost advantage of a no-Teams SKU only exists if you genuinely do not need Teams.
Which Microsoft 365 plan is best for a small business?
Microsoft 365 Business Premium is the standard recommendation for organizations under 300 users that handle sensitive data. It adds Defender for Business, Intune device management, and Entra ID P1 conditional access to the Business Standard feature set, giving small teams enterprise-grade security without a dedicated security hire.
The 300-user cap is the constraint that eventually forces a move. Firms that pass it, or that need unlimited archiving, on-premises rights, or enterprise compliance tooling, move to the E-tier plans. Below that threshold, Business Premium usually costs less than assembling the same endpoint, identity, and device controls from separate products.
What does Microsoft 365 Business Premium include that Business Standard does not?
Business Standard covers the Office applications, email, and collaboration tools. Business Premium adds the security layer: Microsoft Defender for Business endpoint protection, Defender for Office 365 email threat protection, Intune device and application management, Entra ID P1 conditional access, and Purview information protection features.
For a regulated practice, that difference is usually the deciding factor. Conditional access and device management are what let a firm restrict access by device state and location, and enforce controls on personal phones without managing the whole device. Standard has no equivalent, which is why firms in healthcare, finance, legal, and accounting typically land on Premium regardless of headcount.
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