npm install @jtml/core

JSON Token-Minimized Language

Schema-first serialization for LLM prompts. Eliminate key repetition, reduce tokens by up to 60%, and cut API costs — without changing your JSON structure.

JSON Input79 tokens
JTML Output
33 tokens
@schema default
id:i name:s role:s active:b score:f

@data
@array
1|Alice|engineer|1|98.5
2|Bob|designer|0|87.2
3|Carol|manager|1|92

LLM Analysis

Run the same model on both formats simultaneously — your data is interpreted identically, with fewer tokens.

Your API key is never stored on our servers — used only for this request and saved locally in your browser per provider.

Token Analysis

Input Tokens

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Output Tokens

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Token Savings

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Compression

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Cost Calculator

Estimate savings based on your traffic and model pricing.

1,000
100100k

Cost Breakdown — 1,000 req/day on GPT-4o

Encode some JSON above to see cost projections

Zero dependencies

Pure TypeScript. Works in any Node.js 20+ project.

Schema-first encoding

Auto-inferred types. Keys sent once, not per row.

Perfect round-trip

Decode back to the original JSON exactly.