The GPT-4.1 API handles our 600K-token codebase in one call — no chunking, no retrieval glue. The 1M context changed how we ship features.
The GPT-4.1 API is OpenAI's flagship model for coding and instruction following — a 1M-token context window, vision (text + image input), function calling, and structured JSON outputs. The GPT-4.1 API is OpenAI-compatible: point any existing SDK at RouterBase and set the model to gpt-4-1. Input at $1.20 / 1M tokens, output at $4.80 / 1M tokens, cache reads at $0.30 / 1M tokens — 5% below the standard rate, all through one REST endpoint.
Input
GPT-4.1
Hi! I'm a helpful AI assistant. What can I do for you?
GPT-4.1 API: Chat
Use the GPT-4.1 API to run OpenAI's coding-and-instruction model with a 1M-token context window and vision.
The GPT-4.1 API is OpenAI's flagship model for coding and instruction following — a 1M-token context window, 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, set the model to gpt-4-1, and your first call goes through immediately.
Pricing is $1.20 / 1M input tokens, $4.80 / 1M output tokens, and $0.30 / 1M cached-input reads — 5% below the standard rate. One RouterBase key — no separate OpenAI credentials required.
Six reasons teams ship on the GPT-4.1 API
From 1M-token context to 5%-off pricing — what makes GPT-4.1 stand out.
1M-token context
Accepts up to 1 million tokens per request — entire codebases, long documents, or extended chat history fit in a single GPT-4.1 API call.
Vision input
The GPT-4.1 API accepts images alongside text. Pass an image URL or base64 in the same request to caption, extract, or reason over visual content.
Built for coding & instructions
GPT-4.1 is tuned for code generation, diffs, and precise instruction following — strong at agentic coding, refactors, and structured edits.
Function calling & JSON
Define tools and request a JSON schema; the GPT-4.1 API returns structured tool calls and strictly valid JSON for reliable agent and extraction pipelines.
OpenAI-compatible endpoint
The GPT-4.1 API speaks the OpenAI chat-completions wire format. Any Python, Node, Go, or Rust SDK that works with OpenAI works here — just update the base URL.
One key for 200+ models
The same RouterBase key that calls the GPT-4.1 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-4.1 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-4.1 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-4-1. 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-4.1 API
Real production loads running on the GPT-4.1 API and the RouterBase model catalog.
Vision on the GPT-4.1 API let us caption and extract from screenshots in the same call as our text prompts. One pipeline instead of three.
Structured JSON outputs from the GPT-4.1 API killed our flaky parsing — strictly valid JSON every time, and RouterBase made the switch a two-line change.
GPT-4.1's coding quality solved refactors our previous model couldn't touch. Accuracy up 29% on our internal eval — all via the GPT-4.1 API.
A million tokens of context means I can throw the whole repo at the GPT-4.1 API. No more 'context limit exceeded' at 3 AM.
RouterBase puts the GPT-4.1 API and 200+ other models behind one key. Our team stopped filing requests for new provider accounts.
We A/B the GPT-4.1 API against GPT-4o mini per request — same SDK, one model field. Hard coding tasks go to 4.1, the rest stays cheap.
We migrated 42 services to the GPT-4.1 API over a weekend. The only PR comment was 'wait, that's all?'.
At $1.20 / 1M input minus 5%, the GPT-4.1 API made our long-context coding features affordable. The ROI math was instant.
Frequently Asked Questions
Common questions about the GPT-4.1 API.
It is RouterBase's pass-through to OpenAI's GPT-4.1 — a coding-and-instruction chat endpoint with a 1M-token context, vision input, function calling, and structured outputs, served via an OpenAI-compatible REST interface.