AI Context Window Checker
Paste a prompt, document, transcript, or code sample and see which leading AI model context windows can fit the planned request.
Which context windows can hold it?
The status includes your estimated input plus the expected output amount above.
| Model | Context | Max output | Status | Estimated remaining |
|---|
Application frameworks can prepend system messages, tool definitions, memory, retrieved documents, or other hidden context. Leave operational headroom instead of targeting 100% utilization.
A context window is a budget, not a target.
Even when the raw text fits, real applications often add instructions, tool schemas, retrieval context, and conversational history.
For production workloads, measure provider-reported usage and reserve enough space for the output you actually need.
Context-window questions
What is a context window?
It is the token capacity a model can work with for a request, subject to the provider's specific input and output rules.
Should I use the full context limit?
Usually not. Leave headroom for system instructions, tools, retrieval, conversation history, and output.
Is the token estimate exact?
No. The current static version estimates across model families rather than running each provider's exact tokenizer.