GPT-5.1
openai/gpt-5.1The industry reference flagship, top-tier general capability with vision, tools and caching.
Model overview
Context window
400K
tokens
Input price
—
quoted on request
Output price
—
quoted on request
Weekly volume
—
tokens / week
Open weights
No
API only
Capabilities
5
of 11 tags
Description
GPT-5.1 is a language model from OpenAI. Webparam does not stock this model yet and can source it on request — tell us what you need it for and we will come back with availability and a price. OpenAI’s stated focus is the reference point for frontier capability. The weights are not published, so it is API-only.
Capabilities
- Tool calling
- Calls functions you define and returns their arguments as structured data, the basis of agents.
- JSON mode
- Constrains the response to valid JSON matching a schema you supply.
- Streaming
- Emits tokens as they are generated, so answers appear progressively rather than all at once.
- Vision input
- Accepts images alongside text in the prompt.
- Caching
- Reuses already-processed prompt prefixes across requests, cutting input cost for repeated context.
Strengths & weaknesses
Strengths
- Best all-round capability profile
- Mature tooling ecosystem
- Reliable structured outputs
Weaknesses
- Premium output pricing
- Closed weights
Pricing
Free| Rate | Price | Unit |
|---|---|---|
| Input | $0.00 | per 1M tokens |
| Output | — not charged | — |
Prompt caching is supported, so repeated prefixes bill below the listed input rate. Free at the point of use; fair-use rate limits apply to the free tier. Illustrative placeholder pricing.
Context window
400Ktokens
covers prompt and response together, so a long input leaves less room for the answer.
Supported features
| Feature | Support |
|---|---|
| Tool calling | Supported |
| JSON mode | Supported |
| Streaming | Supported |
| Vision input | Supported |
| Audio input | Not supported |
| Long context | Not supported |
| Open weights | Not supported |
| Reasoning | Not supported |
| Fine-tunable | Not supported |
| Batch | Not supported |
| Caching | Supported |
Example use cases
Flagship product features
Best all-round capability profile
Complex assistants
Mature tooling ecosystem
Multimodal apps
Reliable structured outputs
Related models
Comparison
| Attribute | GPT-5.1 | Claude Opus 4.5 | Gemini 3 Pro |
|---|---|---|---|
| Context window | 400K | 200K | 1M |
| Input price | $0.00 | $0.00 | $0.00 |
| Output price | — not charged | — not charged | — not charged |
| Tool calling | Supported | Supported | Supported |
| JSON mode | Supported | Supported | Supported |
| Vision input | Supported | Supported | Supported |
| Open weights | Not supported | Not supported | Not supported |
| Prompt caching | Supported | Supported | Not supported |
Best value in each row is highlighted. Illustrative placeholder data.
Provider information
View OpenAI →OpenAI · San Francisco, United States · est. 2015
OpenAI set the template the whole industry follows, from GPT's scaling curves to the API-first business model every provider now imitates. Its GPT-5 generation and o-series reasoning models remain the benchmark others measure against, and its developer platform is the most imitated interface in AI.
Recent releases
Documentation
Frequently asked questions
Input is billed at $0.00 per 1M tokens, and there is no separate output charge. Prompt caching bills repeated prefixes below the listed input rate. Every figure on this page is an illustrative placeholder.