Gemini vs Claude for Long Documents: Which Model Reads PDFs Best

If your PDF is full of charts, scans or tables, or comes with audio or video, start with Gemini 3.1 Pro. For a contract or report where every claim has to be exact, use Claude Opus 5.5. For everyday reports and research papers, Claude Sonnet 5 costs half as much as Opus and is usually enough. For a large batch of files where speed and cost matter more than depth, run Gemini 3.8 Flash. Whichever model you pick, ask for page numbers and check a few of them before you trust the output.

How to choose a model for long documents

Vendors like to quote context window sizes. That number tells you how much text fits into one request, and says nothing about how well the model reads it. These five criteria matter more:

1. File input. Can you attach the PDF directly, or do you have to extract the text and paste it in? Pasting loses tables, page breaks and anything that lives in an image.
2. Accuracy deep into the text. A model can summarise the first 20 pages perfectly and then blur a clause on page 140. The only way to find out is to ask about details from the middle and the end.
3. Page-level citations. If the model tells you where it found something, you can check it in seconds. If it can't, you have to reread the document.
4. Mixed media. Scanned pages, charts, photos of whiteboards, a recorded meeting that goes with the minutes. Some models take all of this. Others take only text and images.
5. Cost per run. One careful pass over a contract is cheap. Running the same check over 300 invoices is not, and there a cheaper model that's good enough beats an expensive one.

The models below are ordered by input breadth, meaning what you can hand them directly. First come the ones that take files plus audio and video, then the ones that take files and images, and last the one that needs pasted text. Within each group, the more thorough model comes first. If you want to see how Gemini behaves on your own file before reading further, you can try Gemini online and come back.

Gemini vs Claude and the alternatives: comparison table

The credit costs are the per-run prices in Moleculs. If you use the vendors' own apps, check pricing on their sites.

Gemini 3.1 Pro: for PDFs mixed with charts, scans, audio and video

Who it's for: analysts, researchers and anyone whose documents aren't just text. Think quarterly reports with dozens of charts, scanned contracts, slide decks exported to PDF, or a report you want to check against the recording of the meeting where it was presented.

What it does well: it accepts files, images, audio and video in the same request, with up to 16 input images. You can attach a report and ask what each chart shows, whether the numbers in the text match the figures, and which slide a claim came from. On visually heavy files, you don't have to describe the chart to the model yourself.

Where it's limited: at 12 credits per run it costs six times as much as Gemini 3.8 Flash. For a clean, text-only document, you pay for multimodal input you don't use.

When not to use it: for dense legal text where the question is "what exactly does clause 14.3 commit us to". For that kind of task, compare it against Claude Opus 5.5 on your own file.

Gemini 3.8 Flash: for fast, cheap passes over large batches of files

Who it's for: anyone processing many documents rather than studying one. Typical jobs: sorting a folder of supplier PDFs, pulling the same five fields out of every invoice, or getting a one-paragraph summary of each of 50 papers so you know which three to read properly.

What it does well: at 2 credits per run it's the cheapest model in this list, and it accepts the same input types as 3.1 Pro: files, images, audio and video. For extraction with a fixed format ("return the date, the counterparty and the total"), that is usually enough.

Where it's limited: fast models trade depth for speed. Questions that make the model hold two distant sections in mind at once, such as "does the termination clause conflict with the renewal terms", are where it's most likely to miss something.

When not to use it: as the final reader of anything you'll sign. Use it to triage, then pass the documents that matter to a heavier model.

Claude Opus 5.5: for careful reading, contracts and multi-step analysis

Who it's for: lawyers, procurement teams, compliance staff and anyone who needs an answer they can defend. In Moleculs' catalogue, Opus 5.5 is described as Anthropic's flagship for complex reasoning, code and long multi-step tasks.

What it does well: it suits tasks with several steps, like "list every obligation, then group them by party, then flag any that contradict each other". It accepts files and up to 20 images, so a contract with a few scanned annex pages still works. Ask it to quote the clause and give the page number, and you can check the answer line by line.

Where it's limited: at 20 credits per run, it's the most expensive model here. It doesn't accept audio or video, so if the source material includes a recording, use Gemini for that part.

When not to use it: for bulk work or quick "what is this document about" questions. If you want to use Claude in your browser for everyday files, start with Sonnet and move up to Opus when the stakes justify it.

Claude Sonnet 5: the everyday middle ground for reports and research papers

Who it's for: consultants, students writing a thesis, product managers reading market research. These are people who read long documents every week but don't need legal-grade scrutiny on each one.

What it does well: at 10 credits per run it costs half as much as Opus and takes the same input: files and up to 20 images. For summarising a 60-page report, comparing the methods of two papers or drafting a briefing from a long PDF, it's a sensible default.

Where it's limited: on long chains of checks it's less thorough than Opus. If you need every contradiction rather than the obvious ones, the gap shows.

When not to use it: for scan-heavy or chart-heavy files where the meaning is in the images. Try Gemini 3.1 Pro first there. If summaries are your main job, we compare more options in our guide to the best AI for summarizing long documents.

Grok 4.2: when the deciding factor is a very large context window

Who it's for: people with one very long input they don't want to split, such as a full book manuscript, a year of exported correspondence or a large technical specification.

What it does well: xAI positions it around a very large context window and cost efficiency. At 3 credits per run it's cheap, and it accepts files and images, so you can attach the document directly.

Where it's limited: a bigger window fits more text, but not every part of that text gets equal attention. Details buried in the middle are where long-context models tend to slip, so check them.

When not to use it: when your document already fits comfortably into Gemini or Claude. Window size stops mattering then, and reading quality decides.

Kimi K3: long-context reasoning when you paste the text in yourself

Who it's for: people who already have the document as plain text: Markdown exports, transcripts, code documentation or a manuscript in a text file.

What it does well: Moonshot AI's flagship is a multimodal reasoning model with a 1M-token context, according to Moleculs' catalogue. It works as a second opinion on analytical questions about a long text, and at 15 credits per run it sits between Sonnet and Opus.

Where it's limited: in Moleculs it accepts images but not files. You extract the text and paste it in, which strips out layout, tables and page numbers, so page-level citations get much harder.

When not to use it: for scanned PDFs, for anything where layout carries meaning, or when you need to point to a page.

Moleculs: run Gemini and Claude on the same file in one place

Who it's for: people who don't want to pick a winner up front. You can run the same contract through Gemini and Claude and compare the answers without paying for two separate subscriptions.

What it does: Moleculs gives you access to all the models above in one interface under one subscription. Each run costs credits, and the cost is shown next to the model, so you know what a comparison costs before you start. For other file workflows, see our overview of AI tools for working with files.

Where it's limited:

• Moleculs doesn't build models. It provides access to models from Google, Anthropic, xAI, Moonshot AI and others.
• A model in Moleculs isn't guaranteed to behave exactly like the vendor's own app. Settings and the surrounding setup can differ.
• There's no side-by-side view. To compare Gemini and Claude, you run the same file through each model in turn and read the answers yourself.
• There's no public API. All work happens in the interface.

When not to use it: if you only ever use one model and rely on features of that vendor's own app, a direct subscription will suit you better.

Test it yourself: a 6-step check for any long PDF

Vendor claims and benchmark charts won't tell you how a model handles your document. This check will.

1. Pick three facts you already know. Choose one near the start, one in the middle and one near the end of the document. Write them down along with their page numbers.
2. Run the same prompt on two models. For example, Gemini 3.1 Pro and Claude Opus 5.5, or Sonnet 5 if cost matters. You can run this contract-review prompt as a starting point. It asks for every deadline, obligation and penalty with page numbers, then for contradictions between clauses.
3. Ask about your three facts. Ask directly, without hinting at the answer. The middle fact is the one that most often goes missing.
4. Check five citations at random. Open the PDF and confirm each quote is on the cited page. One invented page reference is a warning. Two mean you shouldn't use that model for this document type.
5. Ask a question the document can't answer. A good model says the information isn't there. A weak one makes something up.
6. If answers get vague, split the file. Process the document chapter by chapter and see whether accuracy comes back. If it does, the document is past what that model handles well in one pass.

Note the credit cost of each run, so you know what the better answer cost you.

Which one to pick: by situation

• A contract or agreement you'll sign: Claude Opus 5.5, with page citations checked by hand.
• A report with charts, scans or slides: Gemini 3.1 Pro.
• A document plus the meeting recording or video it refers to: Gemini 3.1 Pro, or Gemini 3.8 Flash if cost matters more. They are the only models in this list that take audio and video.
• Weekly reports and research papers: Claude Sonnet 5 as the default, with Opus for the ones that matter.
• Hundreds of files and the same fields from each: Gemini 3.8 Flash for the first pass, then a heavier model for anything flagged.
• One huge text you don't want to split: Grok 4.2, or Kimi K3 if you already have the text as plain text.
• You don't know yet and want to compare: run your own file through Gemini and Claude using the six steps above, in the vendors' apps or both in Moleculs, and let your document decide.