Glean vs Microsoft 365 Copilot for Enterprise Search

*This research-based comparison was checked against Glean and Microsoft product and administration documentation on September 21, 2026. DiscoverAI did not deploy both products across the same enterprise corpus. Enterprise packaging and contracts require vendor quotes and buyer verification.*

Choose Microsoft 365 Copilot Search when most authoritative work already lives in Microsoft 365 and the organization wants search inside the Microsoft Copilot app. Shortlist Glean when knowledge is spread across Slack, Google Drive, Microsoft 365, Jira, Salesforce, ServiceNow, GitHub, and other systems and an independent enterprise-search layer is the primary goal. Both depend on clean source permissions and connector operations.

| Decision | Glean | Microsoft 365 Copilot Search |
|---|---|---|
| Natural center | Cross-app enterprise knowledge | Microsoft 365 and Microsoft Graph |
| External sources | Native and custom Glean connectors | Copilot connectors ingest external content into Graph |
| User experience | Dedicated search, chat, assistant, and agents | Search module in the Microsoft Copilot app |
| Permissions claim | Fetches source permission maps | Respects underlying permissions and connector ACLs |
| Buying boundary | Quote-based enterprise deployment | Eligible Copilot license; connector capacity can add cost |

Microsoft Copilot Search starts from the Microsoft tenant. It can surface Microsoft 365 content and use connectors for external systems; admins manage connector visibility, crawls, schemas, and restricted content discovery. It is compelling when identity, files, email, meetings, and governance already center on Microsoft.

Glean starts from a heterogeneous application estate. Its connectors parse content and permission maps from many business systems, then feed search, conversational answers, and agents. That can reduce dependence on one productivity suite, but it adds another enterprise index and administrative plane to govern.

Both vendors say they respect source permissions. That does not repair overshared folders, public channels, stale groups, domain-wide links, or excessive service-account access. Enterprise search makes existing access easier to discover; a technically correct result can still expose information the organization never intended to be broadly findable.

Before rollout, inventory sensitive sites, clean group membership, test representative users, and verify deletion and permission-change propagation. Confirm how each connector handles public links, inherited access, external guests, deleted records, private messages, and failed crawls.

Search quality is not a single benchmark. Measure whether the correct source ranks highly, whether answers cite the exact item, whether users can open it, how quickly changes appear, and whether the system abstains when evidence is missing. Tune authoritative sources, titles, schemas, acronyms, bookmarks, and content ownership before blaming the model.

The [Glean review](/articles/glean-ai-review-2026) covers its broader assistant and agent features. Teams should also complete an [AI access inventory](/articles/build-ai-access-inventory-read-write-retain-trigger) before enabling actions.

Choose 100 real questions across HR, IT, sales, engineering, and operations. Include answerable, ambiguous, permission-denied, stale, and unanswerable cases. Score top-three retrieval success, grounded-answer accuracy, citation accessibility, freshness lag, permission leaks, time saved, admin hours, connector failures, adoption, and total cost. Pilot the same source set where possible.

Microsoft Copilot Search is the efficient default for a Microsoft-centered organization. Glean earns the broader shortlist when knowledge spans many systems and enterprise search itself is strategic. Permission hygiene and source quality will determine more of the result than either product demo suggests.