Most “enterprise AI search” comparisons treat Glean, Microsoft Copilot, and Dust as three horses in the same race. They aren’t. They’re three different vehicles, and the reason so many six-figure rollouts stall in pilot is that someone picked the wrong one for their building before the demo even ended.
Here’s the fork that actually decides it: where does your company’s knowledge live? If it’s inside Microsoft 365 and almost nowhere else, that answers most of the question. If it’s smeared across Slack, Confluence, Jira, Salesforce, GitHub, Notion, and forty other tools, that answers it differently. And if what you really want isn’t search at all but a fleet of agents that do things, that’s a third answer entirely.
Let me walk through where each one wins, what it costs when you’re honest about the bill, and the adoption numbers vendors would rather you didn’t dwell on.
The three-way split, in plain terms
Glean is enterprise search first. It crawls your whole tool estate, builds a permissions-aware knowledge graph, and answers questions grounded in company data — then bolts agents on top of that graph.
Microsoft Copilot is task assistance inside the apps you already have open. It drafts the email, summarizes the Teams meeting, builds the PowerPoint. It reasons over your M365 data because it lives inside M365.
Dust is an agent-building platform. It’s for teams who want to design, deploy, and govern custom AI agents across departments — sales, support, engineering — grounded on a curated set of sources. Search is a capability, not the product.
Notice these aren’t competing feature sets. They’re competing worldviews about what an AI layer at work is even for. That’s why “which is best” is the wrong question and “which matches how my company is wired” is the right one.
Microsoft Copilot: the default that only sees half your company
Copilot has a structural advantage nobody else can match: it’s already in the building. If you pay for Microsoft 365, Copilot sits inside Word, Excel, Outlook, and Teams at $30 per user per month on top of your existing licenses. No new vendor, no procurement cycle, no data-residency review with a startup. For a lot of IT leaders that’s the whole pitch, and it’s a good one.
The catch is scope. Copilot sees the Microsoft graph beautifully and everything outside it barely at all. If your engineering team lives in GitHub and Jira, your sales team in Salesforce, your docs in Confluence and Notion — Copilot is looking at a fraction of where the real answers are. It’s a brilliant assistant for the estate Microsoft owns and a bystander to the rest.
And the adoption data is sobering. Microsoft reports over 100 million monthly active Copilot users and says roughly 70% of the Fortune 500 have purchased licenses. But purchased isn’t used. Independent surveys put weekly active usage at only 20–30% of licensed seats, and one measure of workplace conversion landed at about 36% — versus 83% for ChatGPT. Buying the seats turned out to be the easy part.
Why the gap? Gartner warns that roughly half of AI programs stall when the value isn’t obvious, and Forrester found most enterprises are still 12–18 months from scaled deployment, blocked on data readiness and governance more than on the tool itself. Copilot doesn’t fail because it’s bad. It stalls because “we bought Copilot” and “our people changed how they work” are two very different projects, and the second one needs a champion, a budget line, and cleanup on the data Copilot is about to expose.
That last point deserves a flag. Copilot surfaces whatever a user technically has permission to see, which means every over-shared SharePoint folder and stale permission group becomes a discovery risk the day you turn it on. Plenty of rollouts hit pause right there.
Glean: built for the messy, multi-tool reality
Glean is what you reach for when your knowledge isn’t Microsoft-first. It ships 100-plus connectors and indexes across all of them, so a single query pulls from Slack threads, Confluence pages, Jira tickets, Salesforce records, and Google Drive at once — respecting each user’s existing permissions so nobody sees what they shouldn’t. For a company running dozens of SaaS tools, that cross-system retrieval is the thing Copilot structurally can’t do.
The market has noticed. Glean crossed $300 million in ARR in late May 2026, up from $200 million in December 2025 and $100 million only fifteen months earlier — roughly tripling in a little over a year. Its Series F put the valuation at $7.2 billion. More telling than the topline: over 85% of its customers use it across five or more departments, which means it stopped being a search box and became infrastructure. That’s the metric that separates a tool people forget about from one they build workflows on.
Glean has also leaned hard into the cost story. In a year when finance teams are nervous about runaway AI bills, Glean claims it uses about 30% fewer tokens than comparable setups — a pitch aimed squarely at the CFO, not the end user. Whether that holds for your workload is worth testing, but the framing tells you who’s actually signing these deals now.
Pricing is where Glean gets less friendly. It doesn’t publish rates; everything is a custom quote, and the median contract runs around $97,500 a year. Add implementation — enterprise deployments commonly land in the $20,000–$80,000 range for services — and this is a real capital commitment, not a per-seat swipe. Glean makes sense for larger organizations, call it 500-plus users, that genuinely need to search everywhere and can absorb the setup. Below that scale, you’re paying enterprise pricing for capacity you may not use.
Dust: when you don’t want search, you want agents
Dust is the one people miscategorize most. If you go in expecting a Glean clone, you’ll leave confused. Dust is a platform for building teams of AI agents grounded on your company’s knowledge and tools — the product isn’t “ask a question and get an answer,” it’s “design an agent that triages support tickets, or drafts sales follow-ups, or reviews PRs, and govern it over time.”
It’s model-agnostic, so your agents can run on OpenAI, Anthropic, Google, or Mistral depending on the job, and it grounds them through 100-plus connectors — Slack, Notion, GitHub, Salesforce, Zendesk, Snowflake, and the usual suspects — exposed via REST API, MCP servers, and webhooks. That MCP support matters in 2026: it means your Dust agents can plug into the same tool ecosystem everything else is standardizing on.
Two things make Dust genuinely different from the other two. First, the core is open source under an MIT license, and self-hosting is a documented path — rare among workspace AI platforms and a real unlock for teams with strict data or compliance constraints. Second, pricing is approachable: a self-serve Pro plan around $24–29 per user per month, a Max tier at $120 for heavier users, and Enterprise (SSO, SCIM, US/EU data residency) with custom pricing and a 100-user minimum. You can start small and prove value before anyone signs a big contract, which is the opposite of the Glean motion.
The trade-off: Dust asks more of you. Agents don’t build themselves, and the platform is aimed at “AI operators” — people who’ll actually design and maintain these workflows. If you want something that works the moment you flip it on with zero configuration, Dust is more raw material than finished product. That’s a feature if you have the people and a bug if you don’t.
Permissions and governance: the part that quietly sinks pilots
Every one of these tools is only as safe as your access controls, and this is where deployments die more often than on features or price.
The core risk is uniform: an AI assistant that faithfully surfaces everything a user can technically access will happily expose the salary spreadsheet in the mis-permissioned folder, the acquisition doc someone forgot to lock down, the customer list a contractor shouldn’t see. Glean and Dust both enforce permissions at query time so results respect existing access, and Copilot inherits Microsoft’s permission model. None of that saves you if your underlying permissions are a mess — and in most large orgs, they are.
So the real pre-work isn’t choosing a vendor. It’s a permissions audit before you turn any of this on. Budget for it. The teams that skip this step are the ones that pause the rollout in week three after the assistant cheerfully answers a question it never should have.
So which one?
Match the tool to the building, not the demo.
If your company runs on Microsoft 365 and most work happens in Office apps, start with Copilot. It’s already there, it’s $30 a seat, and the integration is genuinely deep. Just go in knowing the hard part is adoption, not purchase — fund the change management and the permissions cleanup, or you’ll join the majority of licenses that get bought and barely touched.
If your knowledge is scattered across a heterogeneous stack of SaaS tools and cross-system search is the actual pain, Glean is the strongest fit — provided you’re at a scale that justifies six-figure contracts and a real implementation. It’s become infrastructure for a reason, and the multi-tool retrieval is something Copilot can’t structurally match.
If what you want is custom agents that take action, or you need open source and self-hosting, or you’d rather prove value at $29 a seat before betting big, Dust is the one — as long as you have the people to build and run the agents it hands you.
The one move that beats all three: run a two-week pilot with your own data and a scorecard that measures sustained weekly usage, not demo-day wow. The vendor that keeps people coming back on your real tool estate is the one worth the contract. Everything else is a slide.
If you’re Microsoft-first and just want to see what Copilot exposes, spin it up for a single team next week — but audit that team’s folder permissions first. What it surfaces will tell you more about your data hygiene than any vendor benchmark will.
Sources: TechCrunch — Glean crosses $300M, Glean Series F announcement, Value Add VC — Copilot adoption data, Dust pricing, Dust GitHub (open source)