Context window checker
Will your document fit GPT-4o, Claude or Gemini? Drop it in and get a straight green-or-red answer — plus a chunk plan if it won't.
Pasting a long document into an LLM and hoping is not a workflow. This tool converts your file in the browser, counts the tokens, and checks them against your selected model's context window. Green means it fits. Red means it doesn't — and you immediately see how it breaks into heading-aware chunks you can export as JSONL. Compare models side by side with the fit chips.
Frequently asked questions
What context windows do you use?+
The published windows for each model (e.g. GPT-4o 128k, Claude 200k, Gemini 1M–2M). They're kept in one place and updated as models change.
What happens if my document is too big?+
You get a red 'doesn't fit' verdict with the overflow amount and a chunk plan — visible boundaries with heading paths, exportable as JSONL.
Does anything upload?+
No. Conversion and counting run entirely in your browser.