What is the best AI for research, citations and fact-checking?

There is no single answer, which is why this page lists 9 of them rather than one. 4 are built specifically for this kind of work; the rest do it well without it being their focus. Start with a free one and change your mind cheaply.

Which of these are free?

6 of the 9 have a genuine free plan you can sign up for today: Gemini Deep Research, NotebookLM, OpenEvidence, Perplexity, ChatGPT deep research, Claude research mode. Free here means a real free tier, not a trial that expires.

How were these chosen?

Every AI product we know of that fits this category is listed, whether or not there is any money in it for us. Ordering is by how well a tool fits the task and whether it has a free plan. Placement is not for sale.

How current are the prices?

Prices were last verified on 31 August 2026. They change often, so confirm on the provider's own pricing page before you spend anything.

Best AI for Research

Search, Research & Academics

Web research, deep research, books, academic papers, citations, news, fact-checking. Typical asks: "What does the evidence say?" "Find me the primary source for this."

Gemini Deep Research Google DeepMind Free plan Built for this

Good for
Runs a multi-step search across dozens of sources and returns a structured, referenced report. Strong first pass on an unfamiliar field.

Watch out
Searches the open web, not scholarly databases. It will miss paywalled literature a library search would find.

Free version
Yes — free to sign up and use

Paid plans
Not verified — check Gemini Deep Research pricing
Open Gemini Deep Research ↗
NotebookLM Google DeepMind Free plan Built for this

Good for
You upload the sources and it answers only from them, linking every sentence to the passage it came from. The strongest verification pattern here.

Watch out
Deliberately limited — it will not answer what your documents do not cover, and cannot tell you whether they are any good.

Free version
Yes — Free, and the core product is not gated
Paid plans
- Higher limits included with Google AI Pro — $19.99/month
Open NotebookLM ↗
OpenEvidence OpenEvidence Free plan Built for this

Good for
Built for clinical literature. Answers cite primary medical research, and it is free for verified clinicians.

Watch out
Medicine only, and access is gated behind clinician verification. No use for a history or engineering student.

Free version
Yes — Free for verified clinicians, ad-supported

Paid plans
No paid tier — it is free
Open OpenEvidence ↗
Perplexity Perplexity Free plan Built for this

Good for
Purpose-built for cited web answers. Every claim carries a numbered link, and Comet extends it across normal browsing.

Watch out
A citation proves a source was consulted, not that it supports the sentence attached to it. Click through on anything that matters.

Free version
Yes — Free tier, limited Pro searches daily
Paid plans
- Pro — $20/month
- Max — $200/month
- Enterprise Pro — $40/person/month
Open Perplexity ↗
ChatGPT deep research OpenAI Free plan Strong fit

Good for
Long autonomous research runs that produce a cited write-up. Useful for scoping a topic before you commit to reading.

Watch out
Web-first rather than database-first. Verify every citation before it enters a bibliography.

Free version
Yes — Free accounts get a small number of deep research runs; paid plans get far more.

Paid plans
Not verified — check ChatGPT deep research pricing
Open ChatGPT deep research ↗
Claude research mode Anthropic Free plan Strong fit

Good for
Holds long papers in context well, which suits close reading and synthesis across several full texts at once.

Watch out
Not connected to indexed scholarly databases.

Free version
Yes — Reading and summarising papers works free; extended multi-step research runs need a paid plan.

Paid plans
Not verified — check Claude research mode pricing
Open Claude research mode ↗
AlphaSense AlphaSense Paid only Strong fit

Good for
Searches licensed filings, broker research and expert-call transcripts. The paid answer to "where does this number come from".

Watch out
Enterprise contract, priced for investment firms. Nothing here for an individual.

Free version
No — paid from the start
Paid plans
- Enterprise only, priced for investment teams
Open AlphaSense ↗
Exa Exa Paid only Strong fit

Good for
A search index built for machines. The right pick if you are building something that needs to retrieve real pages.

Watch out
Developer API only. Nothing here for a non-programmer.

Free version
No — no usable free tier

Paid plans
Not verified — check Exa pricing
Open Exa ↗
Glean Glean Paid only Strong fit

Good for
Searches everything your employer already has — Slack, Drive, Jira, email — with permissions respected.

Watch out
Enterprise sales only. Your IT department has to buy it.

Free version
No — paid from the start
Paid plans
- Enterprise only, priced per seat
Open Glean ↗

Best AI for Research at a glance

Every tool on this page, with whether it has a free plan and who makes it.
Tool	Company	Free plan	Fit
Gemini Deep Research	Google DeepMind	Yes	Built for this
NotebookLM	Google DeepMind	Yes	Built for this
OpenEvidence	OpenEvidence	Yes	Built for this
Perplexity	Perplexity	Yes	Built for this
ChatGPT deep research	OpenAI	Yes	Strong fit
Claude research mode	Anthropic	Yes	Strong fit
AlphaSense	AlphaSense	No	Strong fit
Exa	Exa	No	Strong fit
Glean	Glean	No	Strong fit

Questions

What is the best AI for research, citations and fact-checking?: There is no single answer, which is why this page lists 9 of them rather than one. 4 are built specifically for this kind of work; the rest do it well without it being their focus. Start with a free one and change your mind cheaply.
Which of these are free?: 6 of the 9 have a genuine free plan you can sign up for today: Gemini Deep Research, NotebookLM, OpenEvidence, Perplexity, ChatGPT deep research, Claude research mode. Free here means a real free tier, not a trial that expires.
How were these chosen?: Every AI product we know of that fits this category is listed, whether or not there is any money in it for us. Ordering is by how well a tool fits the task and whether it has a free plan. Placement is not for sale.
How current are the prices?: Prices were last verified on 31 August 2026. They change often, so confirm on the provider's own pricing page before you spend anything.

The other eight categories

Prices last verified 31 August 2026