By Michael Branson, Founder/COO, i3solutions

Quick answer. As of September 2026, if your answers mostly sit in Microsoft 365 and users hold Copilot licenses, choose Copilot; if most sit elsewhere, choose Glean, or both. Microsoft builds its semantic index “for users with a paid Microsoft Copilot license”, and Glean says it “inherits and enforces source-system permissions”.

If a business unit has piloted Glean and wants it funded while the Microsoft account team says Microsoft 365 Copilot includes enterprise search, you are being asked either to pay for one job twice or to pick a side you still have to defend to the risk committee. Engineering knowledge sits in Jira, Confluence and GitHub, sales knowledge in Salesforce, and the policies and contracts in SharePoint. Both vendors say their tools respect source permissions, which means each shows what the source systems already allow. This guide sets out the criteria from each vendor’s own pages, read in September 2026, including the option of running Glean alongside Microsoft 365.

What Each Vendor Says Its Search Does

When the funding request lands, start from what each vendor says its product is, in its own words. Microsoft’s Copilot Search page states: “Microsoft Copilot Search is an AI-powered universal search experience optimized for your organization.” The same page calls it “the single place for quick information across all your Microsoft and non-Microsoft data sources”. Microsoft’s semantic indexing page states: “We generate a semantic index for users with a paid Microsoft Copilot license.” Glean’s connectors page states: “Glean builds indexes and knowledge graphs across your data, so it can understand how your business works and automate work reliably.” Both describe one index across an organization’s knowledge. The decision is which index, over which systems, for which users.

Criterion One: Where the Knowledge Lives

If most of the answers your people look for already sit in SharePoint and the rest of Microsoft 365, the Microsoft index starts where the knowledge is. For content outside it, Microsoft’s Copilot connectors overview states: “External content is stored securely in your tenant, and users only see what they’re allowed to access.” How those connectors are chosen and built is covered in Copilot Integration Architecture: Four Paths, One Sequence. Glean’s homepage displays these source systems beside its headline: Slack, Google Drive, Jira, Confluence, SharePoint, GitHub and Salesforce. List the systems where your people find answers today, mark which sit inside Microsoft 365, and let that list, not either vendor’s demo, set the weight of this criterion.

Criterion Two: Permissions Decide What Either One Shows

If a SharePoint site is overshared today, it is overshared in either tool, because both vendors tie results to the source system’s permissions. Microsoft’s semantic indexing page states: “Microsoft Copilot presents only data that each individual can access using the same underlying controls for data access used in other Microsoft 365 services.” Glean’s connectors page states: “Glean inherits and enforces source-system permissions, so users only see data they’re already allowed to access.” Glean’s security page adds: “Enforce source-system permissions on every read and write; an agent should not automatically access everything the user can.” A source that exposes too much exposes it in either index, so fix the permissions before either one is switched on. SharePoint Permissions Cleanup Before Microsoft 365 Copilot sets out that work.

Criterion Three: Whose License Already Covers the Users

If the people who need answers already hold Microsoft 365 Copilot licenses, the Microsoft index is already being built for them. Microsoft’s semantic indexing page ties the index to the license: “We generate a semantic index for users with a paid Microsoft Copilot license.” Its Copilot Search page states: “If a user has an eligible Microsoft Copilot license, Copilot Search appears as a tab in the Microsoft Copilot app.” When the people asking are a different group, for example engineers outside the Copilot rollout, the license map changes the answer. Microsoft 365 Copilot Licensing: What a Governed Enterprise Deployment Actually Costs covers the Microsoft side of that cost; get Glean’s commercial terms from Glean.

Criterion Four: Where the Index and Data Are Hosted

Before the risk committee asks where the index lives, have each vendor’s own answer on paper. Microsoft’s semantic indexing page states: “User-level index information is stored where the user’s mailbox is located.” Its connectors overview states: “Microsoft hosts the indexing pipeline in the cloud for most connectors.” Glean’s security and architecture documentation lists its deployment options as “SaaS and customer-hosted environments” and points readers deploying in their own cloud to “Review GCP and AWS customer-hosted deployment models and controls.” Glean’s government page says it “supports both cloud and VPC-hosted deployments.” Record each answer as the vendor states it. Whether a location satisfies a residency term or a contract clause is for your compliance owner to decide.

Criterion Five: The Government-Cloud Question

If any of this knowledge sits in GCC, GCC High or DoD, the search decision follows the cloud decision, not the other way round. For Microsoft 365 Copilot in those clouds, including how connectors behave there, Is Your Microsoft Environment Ready for Copilot? What Must Be True First sets out what changes. For Glean, ask Glean in writing for its current authorization status and the boundary it covers before a regulated workload is scoped. Whether a workload must sit in a government cloud, and at which level, is for your compliance owner, your contracting officer and the contract clause to decide. i3solutions does not hold an authorization of its own and does not issue an ATO for any system.

When to Choose Glean

If most of your answers live outside Microsoft 365, choose Glean, or run it alongside Microsoft 365. Choose Glean when the knowledge people search for sits mostly in systems such as Jira, Confluence, GitHub, Salesforce and Slack, and one index across them is the requirement; Glean describes building “indexes and knowledge graphs across your data”. Choose it when a deployment in your own cloud is wanted, since its documentation names “GCP and AWS customer-hosted deployment models and controls.” Choose it when the people who need search are not the people holding Copilot licenses. Run Glean alongside Microsoft 365 when Microsoft 365 Copilot stays the assistant for licensed users and a second index serves the systems outside Microsoft 365. Plan the permissions work once, because both vendors state that results follow the source system’s permissions.

Choosing in One Table

When the steering committee asks why the answer is one platform, the other, or both, one row per option answers it. Each quoted cell is the vendor’s own wording, read in September 2026.

Option What the vendor states Where the knowledge should mostly live Permissions, in the vendor’s words Hosting, in the vendor’s words Confirm with the vendor in writing
Microsoft 365 Copilot “an AI-powered universal search experience optimized for your organization” In Microsoft 365, with connectors for the rest “the same underlying controls for data access used in other Microsoft 365 services” “stored securely in your tenant” Which users hold licenses, and how connectors behave in your cloud
Glean “indexes and knowledge graphs across your data” In systems outside Microsoft 365 “inherits and enforces source-system permissions” “SaaS and customer-hosted environments” Current authorization status and boundary, and the hosting model you need
Both Microsoft 365 Copilot for licensed Microsoft 365 users; Glean across the other systems Split between Microsoft 365 and other systems Both follow the source system’s permissions Two hosting answers to record Which system answers which question, and who owns each index

When This Choice Is the Wrong Frame

If the need is a custom retrieval application over one regulated body of documents, that is a build question, not a search-platform choice, and Custom AI Copilot Development on the Microsoft Stack covers it. If the source permissions are not fixed yet, hold both tools back from indexing anything until they are. If the need is finding records for a legal hold, that is an eDiscovery and retention decision, and a search platform does not settle it.

How i3solutions Answers a Copilot or Glean Decision

When this decision reaches i3solutions, the work starts with a map: each system where your people find answers, who holds which license, and which permissions each source applies today. i3solutions implements the Microsoft technology a customer needs, here Microsoft 365 Copilot, Copilot Search, Copilot connectors and the SharePoint permissions underneath them. On the Copilot side, i3solutions names the cost driver plainly. The order-of-magnitude difference between AI readiness assessment quotes is data governance cleanup: when Dataverse and SharePoint access-control alignment has to precede a Copilot or OpenAI API integration, that remediation dominates the engagement. Delivery is senior and US-based. The work sits within Custom AI Consulting Services for Governed Microsoft Enterprise AI.

Key Takeaways

  • If most of your answers sit in Microsoft 365, start with Microsoft 365 Copilot: Microsoft builds its semantic index “for users with a paid Microsoft Copilot license.”
  • When a source exposes too much, it exposes it in either tool: both vendors tie results to the source system’s permissions, so fix those permissions first.
  • Choose Glean, or run it alongside Microsoft 365, when most answers live in systems such as Jira, Confluence, GitHub and Salesforce.
  • Record each vendor’s hosting answer as stated: Microsoft’s “stored securely in your tenant”; Glean’s “SaaS and customer-hosted environments”.
  • For GCC, GCC High or DoD, settle the cloud first and ask each vendor in writing for its current authorization status.

Frequently Asked Questions

Does Microsoft 365 Copilot include enterprise search?

If your users hold an eligible license, Microsoft’s Copilot Search page states: “If a user has an eligible Microsoft Copilot license, Copilot Search appears as a tab in the Microsoft Copilot app.” The same page describes Copilot Search as “an AI-powered universal search experience optimized for your organization.”

Does Glean enforce the permissions of the source systems?

When you check Glean’s own wording, its connectors page states: “Glean inherits and enforces source-system permissions, so users only see data they’re already allowed to access.” Its security page adds: “Enforce source-system permissions on every read and write; an agent should not automatically access everything the user can.”

Can Glean and Microsoft 365 Copilot run side by side?

If your knowledge is split, you can run Microsoft 365 Copilot for licensed Microsoft 365 users and Glean across systems such as Jira, Confluence and Salesforce, which Glean’s homepage displays among its sources. Both vendors state that results follow the source system’s permissions, so plan the permissions work once.

Where does each one store the index?

When the risk committee asks, Microsoft’s semantic indexing page states: “User-level index information is stored where the user’s mailbox is located.” Glean’s security documentation lists “SaaS and customer-hosted environments” and names “GCP and AWS customer-hosted deployment models and controls.”

Which should come first, the search platform or the permissions cleanup?

If the permissions are not fixed, fix them first: Microsoft states that Copilot uses “the same underlying controls for data access used in other Microsoft 365 services”, and Glean states that it “inherits and enforces source-system permissions”. SharePoint Permissions Cleanup Before Microsoft 365 Copilot covers that work.

Map Where Your Answers Live Before You Fund a Second Index

If the Glean request and the Copilot rollout are both on the budget, bring the list of systems your people search, who holds Microsoft 365 Copilot licenses, and where the risk committee needs the index hosted. The conversation turns that into one recommendation per system: Microsoft 365 Copilot, Glean, or both. Talk to a senior architect

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