01In plain English
In a deep research mode, the AI plans a set of searches, reads many web pages and documents, and then writes a structured report with sources. It works for several minutes rather than answering at once. Tools such as ChatGPT and Gemini offer a mode like this.
02Why it matters when you are choosing
It can turn an afternoon of reading into a draft you can check, which suits market scans, vendor comparisons and background briefs. The report can still contain mistakes, so the value depends on how easy it makes verifying each claim.
03What to check
Check that every claim links to a source you can open, how many reports your plan allows, and whether you can point it at your own documents. Open a few citations to confirm they say what the report claims.
04The tools
7 of the 7 tools we checked offer a deep research mode. Each one is checked against the vendor's own pages. A tool missing from this list may not have been checked yet, which is not the same as a no.
ChatGPT
Claude
Gemini
Perplexity
Mistral
Manus
