JSON Mode & Schema in Ollama

From the Ollama cheat sheet · Structured Output · verified Jul 2026

JSON Mode & Schema

Use the format parameter to get structured JSON responses.

bash

# JSON mode — free-form JSON output
curl http://localhost:11434/api/chat -d '{
  "model": "llama3.2",
  "messages": [{"role": "user", "content": "Tell me about Canada"}],
  "format": "json",
  "stream": false
}'

💡 "format": "json" ensures the model always returns valid JSON

⚡ Pass a JSON Schema object as "format" to enforce an exact output structure

📌 Include format instructions in your prompt too — the model responds better with both

🟢 Schema-based output works best with larger models (7B+) for complex structures

jsonstructuredschema

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