Running on your device · 0 bytes uploaded

Context-window fit checker

Will your prompt fit — and how much room is left for the answer? Exact for OpenAI models, a labeled estimate for everything else.

Model

o200k_base encoding · max output 128,000 tokens

Your prompt

Message 1: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 2: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 3: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 4: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 5: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 6: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 7: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 8: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 9: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 10: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 11: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 12: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 13: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 14: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 15: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 16: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 17: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 18: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 19: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 20: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 21: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 22: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 23: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 24: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 25: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 26: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 27: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 28: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 29: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 30: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 31: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 32: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 33: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 34: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 35: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 36: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 37: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 38: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 39: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.
Message 40: Thanks for reaching out — the export fails when the file exceeds the size limit. Could you split it and try again? I tried splitting it but the second part still fails with the same error.

Fit

Paste a prompt, then press Check fit.

Exact versus estimate

OpenAI rows are exact: the count comes from the model's own encoding, cross-checked against the installed tokenizer package's model catalog. Windows come from that same catalog (snapshot 2026-08-26).
Claude and Gemini have no offline tokenizer here — their rows are a characters÷4 heuristic, labeled estimate, and this tool never calls a vendor API to refine them. Use the custom mode with the vendor's published window.
Providers count differently: some bill the system prompt, tools, and message framing separately, and chat wrappers add tokens per message. Treat every number as a planning check, not an invoice.

Registry sample

gpt-5.6-sol1,050,000 in
gpt-5.6-terra1,050,000 in
gpt-5.6-luna1,050,000 in
gpt-5.6-cyber400,000 in
gpt-5.51,050,000 in
gpt-5.5-pro1,050,000 in
gpt-5.41,050,000 in
gpt-5.4-mini400,000 in
gpt-5.4-nano400,000 in
gpt-5.4-pro1,050,000 in
… 33 models in the dated snapshot

Nothing in yet

Paste, drop, or type to begin. Everything stays on this device.

nothing checks until you press Check fit

All AI tools

Context-window fit checker

Next door in AI