Two different things help with long documents: a big context window that lets the AI read one huge file at once, and a source library that lets it search across many files.
Claude Pro ($20/mo) is the best for reading and analysing long documents carefully. Google AI Pro ($19.99/mo) has the biggest stated context at 1M tokens. If you're juggling dozens of files, NotebookLM handles up to 300 sources per notebook on AI Pro.
| App | Free tier | Paid from | Top plan | Best for |
|---|---|---|---|---|
| Claude | Yes | $20/mo | $100–200/mo | Document analysis, research papers, nuanced writing, software engineering |
| Gemini | Yes | $4.99/mo | $99.99–199.99/mo | Google ecosystem users, video generation, very long documents (1M tokens) |
| NotebookLM (Gemini Notebook) | Yes | $4.99/mo | $99.99–199.99/mo | Students, researchers, and analysts who need grounded answers and audio summaries from their own documents |
| ChatGPT | Yes | $8/mo | $500/mo | Everyday writing, brainstorming, image generation, casual coding |
| Perplexity | Yes | $20/mo | $200/mo | Research with verifiable sources, fact-checking, exploring unfamiliar topics |
Monthly prices in US dollars before tax, from each vendor's official pricing (US list price; weekly-billed plans converted to a monthly figure). Updated October 7, 2026
Document analysis and research papers are Claude's core strengths, and Projects keep a set of long files together across chats. Usage caps are tighter than ChatGPT's, and very long conversations use them faster.
Pick it if: you need careful reading, summaries and critique of long texts.
Full Claude pricing →AI Pro includes a 1M-token context, the largest stated limit among the main assistants, so it can take very long documents in one go.
Pick it if: your files are huge — books, long reports, big data exports.
Full Gemini pricing →Rather than one huge prompt, you build a notebook of sources: 50 per notebook free, 100 with AI Plus, 300 with AI Pro — and answers stay grounded in them.
Pick it if: you have a pile of documents and need answers that stay within them.
Full NotebookLM (Gemini Notebook) pricing →File uploads are included on the free tier, and Plus adds Deep Research and Codex for analysis that goes beyond the file itself.
Pick it if: your documents are moderately long and you want a general assistant.
Full ChatGPT pricing →Pro allows unlimited file uploads, and you can check a document's claims against cited web sources in the same place.
Pick it if: you're fact-checking a document against the web.
Full Perplexity pricing →A context window is how much the AI reads at once — great for one long contract or book. A source library (NotebookLM, Claude Projects) lets you keep many files and ask questions across them. If you have one big file, choose context; if you have many medium ones, choose a library.
Among the main consumer plans, Google AI Pro states a 1M-token context window in Gemini — the largest listed in our data.
Yes. ChatGPT Free includes file uploads, and NotebookLM's free tier lets you add 50 sources per notebook.
How we choose: prices come from each vendor's official pricing page and are re-checked every week. We take no affiliate fees, so rankings aren't for sale.