Moonshot AI just released Kimi K3, and the headline number is hard to ignore: 2.8 trillion parameters, which the company says makes it the largest open-weight model anyone has shipped. The weights are downloadable under the Kimi K3 License, so "free" here means something specific. Free to download and self-host, not free chat credits with no strings attached.
What Kimi K3 actually is
Kimi K3 is a sparse Mixture-of-Experts model with a 1-million-token context window, native visual understanding, and an always-on "thinking mode" built into the model rather than bolted on as a toggle. It's roughly 75% larger than DeepSeek's V4 Pro by parameter count, though sparse MoE models don't activate every parameter per token, so raw size alone doesn't tell you much about actual inference cost.
Three ways to actually get your hands on it
| Method | What you need | Cost |
|---|---|---|
| Self-host from Hugging Face | Serious multi-GPU hardware or a rented cluster | Free weights, you pay for compute |
| Kimi API (OpenAI SDK compatible) | An API key; existing OpenAI or Anthropic tooling works with minor changes | Pay per token |
| Kimi Code CLI | A terminal and the `/model` command to select K3 | Pay per token via API |
The self-host route is the only genuinely free one, and it's not free the way most "free tier" tools on this site are. A 2.8T-parameter model needs enough VRAM across multiple GPUs that most individuals end up renting cloud compute anyway, which puts a real dollar figure on "free." If you just want to try the model without standing up infrastructure, the API is the practical option, and since it's OpenAI SDK compatible, switching existing tooling over is mostly a base-URL change.
How it actually performs
Self-reported benchmarks put K3 ahead of Claude Opus 4.8 max and GPT-5.5 high, though it loses to Claude Fable 5 and GPT-5.6 Sol. On Artificial Analysis's private long-horizon knowledge-work evaluation, K3 scored an Elo of 1547, a jump of 732 points over Kimi K2.6 and second only to Claude Fable 5.
The catch: Semgrep's code security evaluation found K3's headline numbers don't hold up at enterprise scale. On the largest repository in their test set, K3 averaged around 6% F1 for security-relevant code analysis, well behind what the benchmark scores would suggest. If you're evaluating K3 for code review or anything security-sensitive, that gap matters more than the leaderboard position.
Worth trying?
If you're already running open-weight models and have the infrastructure, K3 is worth the download purely for the context window and the jump over Moonshot's own previous release. If you're coming from [Kilo](/tools/kilo) or another lighter open-source coding agent, K3 is a heavier, more capable base model, not a drop-in replacement. You'll need real hardware or a real API budget either way. For casual experimentation, the API is the faster way in.
