By what it does
Search & knowledge retrieval
For search and knowledge retrieval, the strongest pick is Perplexity: current-web answers with citations you can check, free tier included. NotebookLM answers strictly from the documents you give it, which changes what a wrong answer can cost. Glean is the governed, permission-aware option at enterprise scale.
Ranges from enterprise search across every connected app to document-grounded research assistants, web answer engines, internal knowledge agents and general assistants with retrieval. The differentiator is grounding and permissions: enterprise tools enforce source access controls and cite results, reducing hallucination on high-stakes queries.
17 tools fit Search & knowledge retrieval · 13 have a free tier · 2 can run privately
Pick by what you need
The same task, a different best tool depending on the output you want.
Enterprise search
Document grounding
Web answers
Internal knowledge agents
General assistant w/ retrieval
What you can do here
Common workflows people run here.
Recommended tools
Tools in this category, easiest to start with first.
| Tool | Why it fits here | Cost | Ease | Official site |
|---|---|---|---|---|
| AnythingLLM | AnythingLLM is the retrieval option for material that cannot leave the building | Free | Beginner-friendly | Site |
| ChatGPT | ChatGPT turns search into synthesis | Free tier + paid plans | Beginner-friendly | Site |
| Claude | Claude finds, connects and explains information across large document collections | Free tier + paid plans | Beginner-friendly | Site |
| Consensus | Consensus is the fast lane into the academic literature | Free tier + paid plans | Beginner-friendly | Site |
| Google Gemini | Gemini's retrieval strength is reach | Free tier + paid plans | Beginner-friendly | Site |
| Grok (xAI) | Grok's structural advantage in retrieval is native real-time access to X | Free tier + paid plans | Beginner-friendly | Site |
| Kimi | Knowledge retrieval with Kimi has a particular shape: the deep research surface runs the… | Free tier + paid plans | Beginner-friendly | Site |
| Microsoft Copilot | Copilot's retrieval advantage is your own organisation | Free tier + paid plans | Beginner-friendly | Site |
| NotebookLM | NotebookLM is retrieval with the boundaries drawn on purpose | Free tier + paid plans | Beginner-friendly | Site |
| Notion AI | Notion AI answers from your own workspace and connected tools | Free tier + paid plans | Beginner-friendly | Site |
| Perplexity | Perplexity defined answer-first search with citations | Free tier + paid plans | Beginner-friendly | Site |
| Elicit | Elicit is the literature's structured-extraction specialist | Free tier + paid plans | Intermediate | Site |
| Glean | Glean is enterprise search done as a product rather than a feature | Enterprise | Intermediate | Site |
| Guru | Guru stakes out the curated end of enterprise knowledge retrieval: rather than indexing e… | Enterprise | Intermediate | Site |
| Harvey | For search and knowledge retrieval, Harvey's centre of gravity is Vault: it stores, organ… | Enterprise | Intermediate | Site |
| Sana (Workday) | Sana approaches knowledge retrieval through agents that both answer and act | Enterprise | Intermediate | Site |
Also worth a look
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Tools that work together
Stacks for this work
The research-to-deck stack
For consultants, analysts and students who turn source material into presentable conclusions.
CompetitiveThe evidence-grade research stack
For consultants and analysts whose conclusions get challenged, by clients, partners or peer review.
World-ClassThe governed knowledge ops stack
For organisations whose knowledge work must stay inside the tenant, under governance IT signed off.
Where to start
Not sure what to adopt first?
Five quick questions about your job, task and constraints. We'll suggest your top three tools, plus the one to try first.
Common questions
What is the best enterprise AI search tool?
Glean is the category reference: it indexes your organisation's tools and answers questions across them with permission-aware results. It is an enterprise product in procurement and price, sized for large organisations rather than small teams. Smaller teams approximate the value with NotebookLM over curated documents or an assistant with file upload, at a fraction of the commitment.
What is the best tool for document-grounded research?
NotebookLM: upload your sources and it answers strictly from them, with citations pointing back to the exact passage. That grounding converts hallucination risk into a checking task, which is why it suits research, teaching and legal-adjacent work. Its limit is its strength: it knows only what you give it; pair it with Perplexity for open-web questions.
What is the best AI for sourced web answers?
Perplexity: it searches the live web and answers with citations attached, so claims can be checked before they travel into documents and decisions. That sourcing discipline is the difference from a chat assistant's recalled knowledge. Use it for current facts, market questions and anything you would otherwise search manually; verify the sources that matter.
How do AI search tools handle permissions?
The credible ones enforce source permissions: Glean returns only documents the asker could already open, inheriting access controls from each connected system. This is the non-negotiable property to verify before any deployment, because a search layer that leaks across permission boundaries is a breach engine. Test with a restricted document during evaluation, not after rollout.
What is the minimum size for Glean?
Large-organisation scale is the realistic floor: for smaller teams, the procurement process, deployment effort and pricing rarely pay back against lighter alternatives. This is a fit observation, not a hard product limit. Smaller teams get most of the practical value from NotebookLM over curated documents or workspace-native AI search, and can revisit Glean at scale.
Tool facts last checked July 2026