Glean — The Complete Guide

What problem it solves

Company knowledge is scattered across Slack threads, Google Docs, Confluence pages, Jira tickets, email and a dozen SaaS tools. Finding anything requires knowing where it is.

Glean indexes all of it and lets people ask a question in plain language, returning an answer with links to the sources.

Why permissions matter

The hard part is not search — it is search that respects access control. An engineer should not surface the compensation spreadsheet because they asked about salaries.

Glean enforces each source system's permissions per user, so two people asking the same question get different answers based on what they can access. This is the feature that makes enterprise deployment possible at all.

Who it is for

Organisations large enough that knowledge is genuinely lost — typically several hundred employees upward, with many tools in use.

How it works

Connectors index content from each system along with its permission model. Content is chunked and embedded, and a knowledge graph captures relationships between people, documents, teams and projects.

Queries retrieve permitted content, rank it, and generate an answer with citations back to source.

The knowledge graph

Beyond text matching, Glean models who works on what, which documents relate to which projects, and who the expert on a topic is.

That is what allows it to answer "who should I ask about billing migrations" rather than only returning documents containing those words.

Deployment realities

Value depends on connector coverage and on the underlying content being good. Indexing outdated and contradictory documentation produces confidently outdated answers.

Successful rollouts usually involve a content cleanup as much as a technical deployment. Budget for both.

Against building it yourself

The components are available — embeddings, a vector database, a model. Teams routinely underestimate the permission-mapping problem, which is where most internal RAG projects stall.

Mapping and continuously syncing per-document ACLs across a dozen systems is the genuinely hard engineering, not the retrieval.

Against Microsoft and Google alternatives

Microsoft Copilot and Gemini for Workspace do this well within their own ecosystems. Glean's argument is neutrality — most organisations use tools from several vendors.

If your estate is entirely Microsoft or entirely Google, the native option is usually simpler and cheaper.

Why Enterprise Search Projects Disappoint

The technology is rarely the problem. Three organisational conditions decide the outcome and none of them is on the vendor's checklist.

Permissions have to be right first. A search tool that respects your existing access controls will faithfully expose whatever they already got wrong — and the discovery that a shared drive was open to everyone usually arrives via search results. Audit before connecting, not after.

The corpus has to be worth searching. Indexing five years of outdated documents produces confident answers from superseded material. A good answer from a stale document is worse than no answer, because it is believed. Decide what is authoritative and index that.

Someone has to own the gaps. Search reveals what is not written down, which is valuable and actionable only if a person is responsible for acting on it.

And measure it on questions answered, not queries run. Query volume rises when search works badly. Sample real queries, check whether the answer was right, and track that — it is manual, it is the only honest measure, and it is what nobody does.

Adoption, Which Is Where Tools Fail

Most tool decisions are made on capability and lost on adoption. The pattern is consistent enough to plan around.

Name an owner. Not a committee and not "the team" — one person responsible for the configuration, the questions, and whether it is still earning its licence in six months. Tools without an owner decay into a subscription nobody cancels.

Start with one workflow, not the whole team. A narrow deployment that works spreads on its own; a broad one that half-works produces a reputation the tool never recovers from.

Write down what it is not for. The boundary matters more than the capability, because the damage comes from use outside the intended case — and nobody is told where that edge is unless someone writes it down.

Keep the manual path working. For at least one cycle. A team that cannot fall back is a team that cannot report a problem honestly.

Review it on a date you set in advance. Three months, against the criteria you wrote at the start. A tool nobody has reviewed is a tool nobody has decided to keep — and the review is the only thing that ever removes one.