# Context Window Checker

> Paste a document to see whether it fits in the context window of GPT-6, Claude and Gemini models, with room left for the answer. Free, runs in your browser.

Canonical: https://promptitin.com/free-tools/context-window-checker
Last updated: 2026-11-13

Paste a document or open a text file. See how much of each model's context window it fills, and whether there's room left for the answer.

This is an interactive tool. Use it at https://promptitin.com/free-tools/context-window-checker.

## How to use it

1. Paste your text, or open a text file from your computer.
2. Pick how much room to leave for the answer.
3. Check each model. Green fits; red is too long and shows by how much.

## Tips

- The window holds your text and the answer together, so leave room for the reply.
- Models can miss details buried in a very long prompt. Put your question at the end, after the document.
- If a file is too long, split it by chapter or section and ask about one part at a time.
- Cut repeated headers, footers and boilerplate before pasting. They use tokens and add nothing.

## FAQ

### What is a context window?

The most text a model can take in at once, counted in tokens. It includes your prompt, any documents, earlier messages and the answer.

### How big are today's context windows?

The current models from OpenAI, Anthropic and Google all take about 1 million tokens through their APIs. That's roughly 750,000 words.

### Why does ChatGPT say my text is too long when it fits here?

Chat apps can set lower limits per message than the API window. If that happens, split the text into parts.

### Is my document uploaded?

No. Files are read in your browser and nothing leaves your device.

## Related

- [AI Token Counter](https://promptitin.com/free-tools/ai-token-counter)
- [AI API Cost Calculator](https://promptitin.com/free-tools/ai-api-cost-calculator)
- [ChatGPT Character Counter](https://promptitin.com/free-tools/chatgpt-character-counter)