nemotron-3-ultra-550b-a55b-free
Nemotron 3 Ultra (free) is NVIDIA’s open frontier reasoning and orchestration model, a hybrid Transformer-Mamba mixture-of-experts with 55B active out of 550B total parameters. This is the free tier served through OpenRouter: requests are rate-limited, the free version may be withdrawn at any time, and free providers may log prompts — use the paid version for production.
Pricing: Input 0 credits / 1M tokens (≈ $0.00), Output 0 credits / 1M tokens (≈ $0.00).
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Nemotron 3 Ultra (free) is NVIDIA’s open frontier reasoning and orchestration model, a hybrid Transformer-Mamba mixture-of-experts with 55B active out of 550B total parameters. This is the free tier served through OpenRouter: requests are rate-limited, the free version may be withdrawn at any time, and free providers may log prompts — use the paid version for production.
Nemotron 3 Ultra (free) at a glance
Nemotron 3 Ultra (free) is a chat model from NVIDIA. It accepts text as input and returns text, with a context window of up to 1M tokens.
Use it without hosting anything
The same key also works for the other chat, image, video and audio models on ModelFold.
Core Capabilities of Nemotron 3 Ultra (free)
Up to 1M tokens of context
Keep long conversations, large documents and sizeable code in a single request, so the model can reason over the full material instead of fragments.
Function calling
Nemotron 3 Ultra (free) supports tool (function) calling: describe your functions in the request and the model returns structured calls your code can run — the basis for agents and integrations.
Adjustable reasoning effort
Choose a reasoning effort level (low, medium or high) per request to balance depth of thinking against speed and token usage.
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Step 1: Try it in the Playground
Open the Playground at the top of this page, type a prompt and see how Nemotron 3 Ultra (free) responds before writing any code.
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Step 2: Create an API key
Sign in to ModelFold and create an API key in the console. Keep it secret and send it as a Bearer token.
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Step 3: Send a request
Call POST https://modelfold.ai/v1/chat/completions with "model": "nemotron-3-ultra-550b-a55b-free" and your messages. Existing OpenAI-compatible SDKs work by changing the base URL and key.
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Step 4: Ship and monitor
Integrate the response into your product and check token usage and spend for every call in the console logs.
Analysis and complex reasoning
Work through research questions, data interpretation, planning and other problems that need careful step-by-step reasoning.
Autonomous agents
Build agents that plan multi-step tasks, call your tools and APIs, and keep working toward a goal across long sessions.
Long-document workflows
Feed in long reports, contracts, manuals or codebases and ask for summaries, comparisons and answers grounded in the material.
Frequently Asked Questions
What is Nemotron 3 Ultra (free)?⌄
Nemotron 3 Ultra (free) is NVIDIA’s open frontier reasoning and orchestration model, a hybrid Transformer-Mamba mixture-of-experts with 55B active out of 550B total parameters. This is the free tier served through OpenRouter: requests are rate-limited, the free version may be withdrawn at any time, and free providers may log prompts — use the paid version for production.
Which inputs does Nemotron 3 Ultra (free) support?⌄
Nemotron 3 Ultra (free) accepts text and returns text. Through ModelFold you send text messages; documents attached in the Playground are converted to text.
How long is the context window of Nemotron 3 Ultra (free)?⌄
Up to 1M tokens, shared between your input and the model’s output.
Does Nemotron 3 Ultra (free) support function calling?⌄
Yes. Nemotron 3 Ultra (free) supports tools / function calling through the standard tools parameter of the chat completions API.
How is Nemotron 3 Ultra (free) billed on ModelFold?⌄
This is the free version served through OpenRouter: calls are not charged, but they are rate-limited and the free version may be withdrawn at any time. Use the paid version of the model for production traffic.
| Input | 0 credits 1M tokens≈ $0.00 |
| Output | 0 credits 1M tokens≈ $0.00 |
Billed per token: input and output are priced separately, and thinking tokens count as output. The Playground charges exactly the same way.
Read API docs →AI Agents · Claude Code / Cursor / Trae →curl https://modelfold.ai/v1/chat/completions \
-H "Authorization: Bearer $MODELFOLD_API_KEY" \
-H "Content-Type: application/json" \
-d '{"model":"nemotron-3-ultra-550b-a55b-free","messages":[{"role":"user","content":"Hello"}]}'