Definition
Active parameters are the weights a model actually uses to produce each token. In a dense model, every parameter is used every time, so active equals total. In a mixture-of-experts (MoE) model, a small router picks a few "experts" for each token and skips the rest, so only a fraction of the weights do work on any given step. Model names now often carry both numbers. Mistral's Hugging Face repo for Large 4 is Mistral-Large-4-1T-A52B: about 1 trillion total, about 52 billion active.
Recent Examples
| Model | Total | Active per token | Released |
|---|---|---|---|
| Mistral Large 4 | About 1T | 49B (52B counting embedding and output layers) | Open weights October 29, 2026 |
| Muse Spark Open (Meta) | 816B | 42B | October 15, 2026 |
| Reflection Beam | 501B | 23B | Weights October 16, 2026 |
| Gemma 4 26B-A4B (Google) | 26B | 4B | 2026 |
Mistral's model card describes 128 routed experts with 4 active per token plus 1 shared expert. Coverage disagrees on the exact figures (1T or 1.05T total, 49B or 52B active), mostly because of what is counted.
What Each Number Controls
- Active parameters set speed and compute cost. Fewer active weights per token means less arithmetic and less memory read per token, so a 1T MoE can generate faster than a dense 400B model.
- Total parameters set memory. Every expert must be loaded, because the router can pick any of them. A 1T model needs memory for all 1T weights, at whatever precision you run it.
That second point is the one people miss. A model with "only 42B active" still won't fit on a 128 GB laptop if it has 816B total. See how much RAM each open-weight model needs and running Mistral Large 4 locally.
Why It Matters for AI Visibility
Cheap active compute is why very large open models now run inside companies, national clouds and agent products at low prices. Their answers are not observable from outside, so what they learned about your brand at training time is what those users get. Size also affects knowledge: larger total parameter counts tend to retain more long-tail facts, which includes smaller brands.