We route 90% of our traffic through the GPT-4o mini API — classification and extraction at a fraction of the cost. The 5% RouterBase discount is pure margin.
The GPT-4o mini API is OpenAI's fast, low-cost multimodal model — a 128K-token context window, native vision (text + image input), function calling, and structured JSON outputs. The GPT-4o mini API is OpenAI-compatible: point any existing SDK at RouterBase and keep the model name gpt-4o-mini. Input at $0.09 / 1M tokens, output at $0.36 / 1M tokens, cache reads at $0.045 / 1M tokens — 5% below the standard rate, all through one REST endpoint.
Input
GPT-4o mini
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GPT-4o mini API: Chat
Use the GPT-4o mini API to run OpenAI's fast, low-cost multimodal model — text and vision in one endpoint.
The GPT-4o mini API is OpenAI's most cost-efficient small model — a 128K-token context window, native vision (text + image input), function calling, and structured JSON outputs. Routed through RouterBase, it is fully OpenAI-compatible: point any existing SDK at RouterBase's base URL, keep the model name gpt-4o-mini, and your first call goes through immediately.
Pricing is $0.09 / 1M input tokens, $0.36 / 1M output tokens, and $0.045 / 1M cached-input reads — 5% below the standard rate. One RouterBase key — no separate OpenAI credentials required.
Six reasons teams ship on the GPT-4o mini API
From native vision to 5%-off pricing — what makes GPT-4o mini stand out.
128K-token context
Accepts up to 128,000 tokens per request — long documents, multi-file code, or extended chat history fit in a single GPT-4o mini API call.
Native vision
The GPT-4o mini API accepts images alongside text. Pass an image URL or base64 in the same request to caption, extract, or reason over visual content.
Function calling & tools
Define tools and the GPT-4o mini API returns structured tool calls — wire it into agents, retrieval, or app actions with the standard OpenAI function-calling schema.
Structured JSON outputs
Request a JSON schema and the GPT-4o mini API returns strictly valid JSON every time — no brittle parsing, ideal for extraction and classification.
Fast & low-cost
Built for high-volume workloads: the GPT-4o mini API is OpenAI's cheapest GPT-4-class model at $0.09 / 1M input tokens — 5% below the standard rate through RouterBase.
One key for 200+ models
The same RouterBase key that calls the GPT-4o mini API also routes to GPT-5, Claude Opus 4.8, Gemini 3.5 Flash, and 200+ other models — no per-provider credential management.
Quickstart
Get started with the GPT-4o mini API in 3 steps
From sign-up to your first response in under 5 minutes.
Create a RouterBase API key
Sign up and generate an API key — one key reaches the GPT-4o mini API and every other model in the catalog.
Send your first message
Point any OpenAI-compatible SDK at routerbase.com/v1 and set the model to gpt-4o-mini. The response follows the standard chat-completions schema — streaming and vision supported.
Inspect usage
Every response includes a detailed token breakdown — input, output, and cache-read tokens — so cost and cache-hit rate are visible on every call.
Pay only for what you use
RouterBase passes through partner-tier pricing. Compared against the model's official published API rate.
What teams build with the GPT-4o mini API
Real production loads running on the GPT-4o mini API and the RouterBase model catalog.
Native vision on the GPT-4o mini API replaced a whole OCR pipeline. One call captions and extracts — text and image in the same request.
Structured JSON outputs from the GPT-4o mini API killed our flaky regex parsing. Strictly valid JSON every time, zero retries.
At our volume, GPT-4o mini is the only GPT-4-class model that pencils out. RouterBase makes it 5% cheaper still.
Function calling on the GPT-4o mini API wires straight into my agent loop. Cheap enough that I stopped counting tokens.
RouterBase puts the GPT-4o mini API and 200+ other models behind one key. Our team stopped filing requests for new provider accounts.
We A/B the GPT-4o mini API against GPT-4o per request — same SDK, one model field. Most traffic stays on mini and the bill dropped 70%.
We migrated 42 services to the GPT-4o mini API over a weekend. The only PR comment was 'wait, that's all?'.
At $0.09 / 1M input minus 5%, the GPT-4o mini API made our high-volume features actually profitable. The ROI math was instant.
Frequently Asked Questions
Common questions about the GPT-4o mini API.
It is RouterBase's pass-through to OpenAI's GPT-4o mini — a fast, low-cost multimodal chat endpoint with a 128K-token context, native vision, function calling, and structured outputs, served via an OpenAI-compatible REST interface.