Model comparison
GPT OSS 20B (free) vs Kimi K3
GPT OSS 20B (free) (OpenAI) and Kimi K3 (Moonshot) side by side: what each costs per million tokens through Rapid Router, how much context each takes, what each supports, and where independent benchmarks place them. Same API, same key; switching is a one-string change.
| GPT OSS 20B (free) | Kimi K3 | |
|---|---|---|
| Input price per 1M | $0.030 | $0.304 |
| Output price per 1M | $0.140 | $11.94 |
| Context window | 131K tokens | 1M tokens |
| Max output | 16K tokens | 131K tokens |
| Input types | text | text, image, video |
| Capabilities | tools, reasoning | tools, JSON, vision, reasoning |
| Author | OpenAI | Moonshot |
What a month costs on each
| Workload | GPT OSS 20B (free) | Kimi K3 |
|---|---|---|
| Chatbot month (15M in, 4M out) | $1.01 | $52.30 |
| RAG month (40M in, 3M out) | $1.62 | $47.97 |
| Coding month (60M in, 10M out) | $3.20 | $137.60 |
On a typical 75/25 input-output mix, GPT OSS 20B (free) costs less (about 98% less than Kimi K3). Kimi K3 takes the longer prompt at 1M tokens. Try your own numbers in the cost calculator.
Call either one
curl https://rapidrouter.ai/api/v1/chat/completions \
-H "Authorization: Bearer $RAPIDROUTER_API_KEY" \
-H "Content-Type: application/json" \
-d '{"model": "openai/gpt-oss-20b:free", "messages": [{"role": "user", "content": "Hello"}]}'
# the other one: change the model string
-d '{"model": "moonshotai/kimi-k3", ...}'Common questions
Which is cheaper, GPT OSS 20B (free) or Kimi K3?
GPT OSS 20B (free) is cheaper on a typical mix of 75% input and 25% output tokens, by about 98%. Through Rapid Router both are billed at the provider list price per million tokens.
Which has the larger context window?
Kimi K3, at 1M tokens. GPT OSS 20B (free) offers 131K tokens.
Can I switch between GPT OSS 20B (free) and Kimi K3 without changing code?
Yes. Both are callable at https://rapidrouter.ai/api/v1 with the same OpenAI-compatible request; only the model string changes (openai/gpt-oss-20b:free or moonshotai/kimi-k3).
How do I pay for GPT OSS 20B (free) or Kimi K3?
Top up a Rapid Router balance by card in US dollars, and both models debit that balance per request.
More GPT models: OpenAI API pricing · More Kimi: Moonshot API pricing