Get started with APIStack

1:18

Prefer video? · 1:18

Getting started: account, API key and first call

Create a free account, find your API key, run a real request and see it counted in your usage.

All video tutorials →Watch on YouTube ↗

1. Create a free account (1,000 calls/month, no card).
2. Copy your API key from the dashboard.
3. Make a call. This example Base64-encodes a string:

curl -X POST https://apistack.online/api/utilities/base64/v1 \
  -H "x-api-key: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"operation": "encode", "text": "Hello, world"}'

const response = await fetch('https://apistack.online/api/utilities/base64/v1', {
  method: 'POST',
  headers: {
    'x-api-key': process.env.APISTACK_API_KEY,
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({ operation: 'encode', text: 'Hello, world' })
})
const data = await response.json()
console.log(data)

import os, requests

response = requests.post(
    "https://apistack.online/api/utilities/base64/v1",
    headers={"x-api-key": os.environ["APISTACK_API_KEY"]},
    json={"operation": "encode", "text": "Hello, world"},
)
print(response.json())

Want to try without an account first? Use Try Free.

Prefer Postman, Insomnia or code generation? Import the OpenAPI 3.0 spec for all APIs.

Send your API key in the x-api-key header on every request:

x-api-key: YOUR_API_KEY

Keep keys on the server. Don't put them in browser or mobile code, and don't commit them to git. If a key leaks, generate a new key in the dashboard and delete the old one; a deleted key stops working immediately.

Responses are JSON. Successful calls return "success": true with the result. Errors use HTTP status codes and a consistent body:

{
  "success": false,
  "error": "Invalid API key",
  "code": "INVALID_API_KEY",
  "message": "The provided API key is invalid or inactive. Please check your API key and try again."
}

Each plan has a monthly call quota shared across all APIs, plus a per-minute rate limit:

Responses include X-RateLimit-Limit, X-RateLimit-Remaining and X-RateLimit-Reset headers. On a 429, wait until the reset time and retry. We email you at 80% and 100% of your monthly quota. See pricing for upgrades and top-ups.

Every API is available to AI agents (Claude, ChatGPT, Cursor, VS Code…) through one Model Context Protocol endpoint, using the same API key, plan access and quota:

https://apistack.online/api/mcp/connect

It exposes three tools: search_apis, get_api_details and call_api. Add ?categories=finance or ?apis=slug1,slug2 to get one tool per API instead. Example for Claude Code:

claude mcp add --transport http apistack https://apistack.online/api/mcp/connect \
  --header "x-api-key: YOUR_API_KEY"

Setup for Cursor, VS Code and Claude Desktop is on the MCP page, along with the dedicated per-API servers.

All APIs are also listed on RapidAPI. If you subscribe there, call the RapidAPI endpoint with your RapidAPI key; billing and quotas are handled by RapidAPI. The APIs and responses are the same.

Questions or problems? Email support@apistack.online with the endpoint, the request you sent and the response you got.