Best LLM for JSON / Structured Output
Ranked on JSON-mode reliability, schema-adherence, and price. Failures here tax the rest of your pipeline.
Updated April 2026. Top 3 this month: DeepSeek: R1 0528, Qwen: Qwen3.5 Plus 2026-02-15, DeepSeek: DeepSeek V3.
How we rank
Structured outputs — JSON, XML, YAML — look simple and are not. Models that are strong at prose can still fail to emit valid JSON under pressure. We weight JSON-mode support and schema adherence, then price; for agentic pipelines JSON reliability is often a bigger efficiency lever than raw reasoning.
Pillars and weights: JSON mode (50%) · schema adherence (30%) · price (20%). Our full methodology is published on the methodology page.
Top ranked models
| Rank | Model | Provider | Input $/1M | Output $/1M | Context |
|---|---|---|---|---|---|
| 1 | DeepSeek: R1 0528 | DeepSeek | $0.50 | $2.15 | 163,840 |
| 2 | Qwen: Qwen3.5 Plus 2026-02-15 | Qwen | $0.26 | $1.56 | 1,000,000 |
| 3 | DeepSeek: DeepSeek V3 | DeepSeek | $0.32 | $0.89 | 163,840 |
| 4 | Qwen: Qwen3.5 397B A17B | Qwen | $0.39 | $2.34 | 262,144 |
| 5 | Tencent: Hunyuan A13B Instruct | Tencent | $0.14 | $0.57 | 131,072 |
| 6 | MiniMax: MiniMax M2.1 | MiniMax | $0.29 | $0.95 | 196,608 |
| 7 | Arcee AI: Trinity Large Preview | Arcee AI | $0.00 | $0.00 | 131,000 |
| 8 | OpenAI: GPT-4o (2024-11-20) | OpenAI | $2.50 | $10.00 | 128,000 |
| 9 | MiniMax: MiniMax-01 | MiniMax | $0.20 | $1.10 | 1,000,192 |
| 10 | Anthropic: Claude Sonnet 4.5 | Anthropic | $3.00 | $15.00 | 1,000,000 |
Tips for json / structured output
- Always send a schema. Most modern models support a constrained output mode.
- Validate server-side. Never trust the model to handle `null` vs. `undefined` correctly.
- If you see repeated schema violations, switch to function-calling rather than free-form JSON.
Frequently asked questions
Which LLM produces the most reliable JSON?
As of April 2026, our weighted top 3 are DeepSeek: R1 0528, Qwen: Qwen3.5 Plus 2026-02-15, DeepSeek: DeepSeek V3.
JSON mode vs function calling?
Function calling is stricter and preferred for agent tools. JSON mode is fine for single-shot extraction.
Should I include a schema in the prompt?
Yes — even if your provider supports constrained decoding, an in-prompt schema reduces post-generation errors.
Related tasks
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Data refreshed daily via our snapshot cron. See our public JSON API for programmatic access.