Context Window Packer
Fit as many RAG chunks as possible into a model context budget.
Chunks (separated by your delimiter)
Packed context
SYSTEM: You answer using only the supplied context. CONTEXT: [1] Chunk 1: The billing API returns 402 when the subscription lapsed. [2] Chunk 2: Retries use exponential backoff starting at 500ms. [3] Chunk 3: Webhooks are signed with HMAC-SHA256 using the endpoint secret. QUESTION: Why did the payment fail?
About the Context Window Packer
Split your retrieved chunks by a delimiter, set the system prompt, question and reply reservation, then let the packer greedily fill the remaining context window. It numbers the included chunks, shows exactly which ones were dropped and exports the final prompt ready to send.
Examples
3 chunks
3 retrieved passages + questionOutput
All 3 packed — 231 / 128,000 tokensKeyboard shortcuts
- Copy the main outputCtrl / ⌘ + Shift + C
- Download the resultCtrl / ⌘ + S
- Share this toolCtrl / ⌘ + Shift + S
- Reset the inputsAlt + R
- Open the tool search paletteCtrl / ⌘ + K
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Frequently asked questions
Read more
- How LLM tokens really work (and why your word count is a bad estimate)
BPE splits words, punctuation and whitespace into pieces. Here is how tokens are counted, why context windows overflow, and how to plan a prompt that fits.
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Version 1.0.0 · Updated 2026-08-15 · Runs entirely in your browser