StepFun: Step 5 Preview (free)
Step 5 Preview (free) is a reasoning model from StepFun released on Aug 26, 2025. It reads text and images and writes text, with a 1M token context window and up to 64K tokens per reply.
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It costs $0 per million input tokens and $0 per million output tokens.
It supports tool calling and prompt caching.
- Modalities
- In / out price
- $0 / $0 per 1M
- Context
- 1M
- Max output
- 64K
- Released
- Aug 26, 2025
- Knowledge cutoff
- n/a
- Tool calling
- Structured output
- Reasoning
- Prompt caching
- Open weights
- Free to use
Step 5 Preview (free) pricing
USD, as listed on Oct 15, 2026. Most bills are input heavy, so the cached input rate matters as much as the headline price.
| Input | $0 / 1M tokens | |
|---|---|---|
| Output | $0 / 1M tokens | |
| Cached input (read) | $0 / 1M tokens |
What Step 5 Preview (free) costs per month
Pick a workload close to yours or type your own volumes.
Supported request parameters
What you can set when you call Step 5 Preview (free) through an OpenAI compatible API.
- Tools
tools - Reasoning
reasoning - Temperature
temperature
Alternatives to Step 5 Preview (free)
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Step 5 Preview (free) questions
How much does the Step 5 Preview (free) API cost?
$0 per million input tokens and $0 per million output tokens, with cached input at $0. The estimator on this page turns that into a monthly bill for your own workload.
What is the context window of Step 5 Preview (free)?
1,000,000 tokens of input, and it can write up to 64,000 tokens in one reply. As a rough guide, a million tokens is around 750,000 English words.
Does Step 5 Preview (free) support tool calling?
Yes. It accepts tool definitions, which is what an agent needs to call your APIs.
Is Step 5 Preview (free) open source?
No. StepFun serves it through an API only, so you cannot download the weights or host it yourself.
When was Step 5 Preview (free) released?
Aug 26, 2025.
Catalog data from models.dev (MIT licensed), refreshed daily, last on Oct 15, 2026. The summary is written from these facts.