Access and use GPT‑4.1's API. 5 minutes, tops.

Introduction to GPT‑4.1

GPT‑4.1 is OpenAI’s brand‑new flagship model for 2025. It speaks text and images, handles a mind‑blowing 1,000,000‑token window per request, and still answers faster than GPT‑4o. Even better, it costs less. (See pricing below.)

If you are new to large language models, take a moment to skim my plain‑English explainer on how GPT‑style LLMs work. It will save you headaches later.

Ready to roll? Let’s build your first GPT‑4.1 request.

Create an account to get your GPT‑4.1 API key

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Creating an account on OpenAI

Confirm your email address.
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Open the Billing overview page and add credit or a payment method so your keys work right away. (The free‑credit program ended mid‑2024.)

Adding credit so the key works right away

Generate your first API key for GPT‑4.1. Keys are shown once; paste it into a password manager immediately.

API key generation on OpenAI

Got your key? Great. Time to hit the API.

How to make your first request to GPT‑4.1

Open your terminal and run this cURL snippet:

macOS and Linux:

curl -X POST \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $OPENAI_API_KEY" \
  https://api.openai.com/v1/chat/completions -d '{
    "model": "gpt-4.1",
    "messages": [
      { "role": "system", "content": "You are an assistant." },
      { "role": "user", "content": "Hello!" }
    ]
  }'

Windows command prompt (one‑liner):

curl -X POST -H "Content-Type: application/json" -H "Authorization: Bearer %OPENAI_API_KEY%" https://api.openai.com/v1/chat/completions -d "{ \"model\": \"gpt‑4.1\", \"messages\": [{\"role\":\"user\",\"content\":\"Hello!\"}] }"

Pro tip: The alias gpt‑4.1 always points at the newest 4.1 weights, so you enjoy silent upgrades.

Token budget: a single call can swallow up to 1,000,000 tokens (roughly 750,000 English words).

How to enable JSON mode with GPT‑4.1

GPT‑4.1 obeys JSON schemas the same way GPT‑4o did. Add a response_format field and you get rock‑solid JSON every time.

curl -X POST \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $OPENAI_API_KEY" \
  https://api.openai.com/v1/chat/completions -d '{
    "model": "gpt-4.1",
    "messages": [
      { "role": "system", "content": "Serve answers as tight JSON." },
      { "role": "user", "content": "Solve 8x + 31 = 2." }
    ],
    "response_format": {
      "type": "json_schema",
      "json_schema": {
        "strict": true,
        "schema": {
          "type": "object",
          "properties": {
            "steps": { "type": "array", "items": { "type": "string" } },
            "final_answer": { "type": "string" }
          },
          "required": ["steps", "final_answer"],
          "additionalProperties": false
        }
      }
    }
  }'

Keep schemas lean; every character counts against your million‑token window.

GPT‑4.1 pricing

Model	Input (per 1 M)	Output (per 1 M)
gpt‑4.1 (1 M context)	$2.00	$8.00
gpt‑4.1‑mini (1 M context)	$0.40	$1.60
gpt‑4.1‑nano (1 M context)	$0.10	$0.40

(For comparison, GPT‑4o now costs $5 in and $15 out.)

Ten project ideas unlocked by GPT‑4.1

Whole‑repo refactorers: Feed the model your monolith and an upgrade brief; get back pull requests instead of single‑file rewrites.
Legal discovery copilots: Drop in gigabytes of PDFs and ask clarifying questions.
Enterprise memory chatbots: Keep every support ticket ever written in the prompt and never ask customers to repeat themselves.
Code compliance auditors: Scan enormous codebases for OWASP issues without paging in files one by one.
Million‑token storyboards: Hand GPT‑4.1 a screenplay and all storyboard sketches; receive continuity‑checked shot lists.
Financial data wranglers: Parse multi‑sheet Excel workbooks, cross‑match with SEC filings, and spit out red‑flag reports.
Video essay assistants: Upload lecture videos with transcripts, then query them live during study sessions.
Long‑term personal journals: Store years of journaling data and let the model surface patterns and throwbacks.
Multi‑doc contract generators: Provide prior agreements and a term sheet; receive a draft contract that references legacy clauses correctly.
Mega‑scale RAG pipelines: Chunk millions of tokens from your company wiki and ask real‑time questions without an external vector DB.