Fibonacci Generator API

About the Fibonacci Generator API

Fibonacci Generator returns Fibonacci numbers using the classic rule where each number is the sum of the two preceding ones. Ask for a fixed count of terms, or for every term up to a ceiling value, and optionally begin later in the sequence instead of at zero. Each response carries the sequence itself, its first and last values, the sum, the most recent ratios between neighbouring terms and the golden ratio approximation those ratios converge on.

It is used to seed math exercises and coding tests, to build Fibonacci retracement levels or spacing scales, to generate test data for number sequence functions, and to show students how quickly the ratio settles near 1.618.

Every field is available on the Free plan. Terms are computed exactly on the server; only very large terms lose their last digits when written out as JSON numbers.

How it works

The Fibonacci Generator has two modes that share one response shape. With count (1 to 1000) it returns that many terms. With maxvalue it returns every term that does not exceed the ceiling, with a hard stop at 5,000 terms. startfrom (0 to 10,000) advances the generator before output begins. At the default of 0 the sequence opens with 0, 1, 1, 2 and the leading 0 counts toward count; at any higher value the first term returned is F(startfrom + 1), so startfrom=10 begins at 89.

Terms and the running sum are accumulated as exact big integers and converted to JSON numbers only when the response is built. A JSON number holds integers exactly only up to 2^53, so from F(79) onward the returned digits are the nearest representable value rather than the exact term, and beyond roughly F(1476) a term is too large for a number at all and serialises as null. For exact large values, use the sequence for its shape and compute the digits client-side.

ratios divides each term by the one before it, skipping any division by zero, rounds to six decimal places and keeps only the last five. golden_ratio_approximation is the final ratio, or null when the sequence is too short to form one, for example a single term. first_value, last_value and count describe the returned array, and start_from echoes the offset used.

What people use it for

Math Education

Teach Fibonacci sequences and golden ratio concepts in educational applications and tools

Algorithm Testing

Generate test data for algorithms and performance testing using Fibonacci sequences

Visual Design

Apply Fibonacci ratios and golden ratio proportions in design and layout calculations

Data Analysis

Use Fibonacci numbers in technical analysis, trading algorithms, and pattern recognition

Ways to call it

One endpoint, many ways in — REST with JSON, XML, YAML and CSV, plus GraphQL and an MCP interface for AI agents.

JSON

Default REST response

XML

Markup format

YAML

Human-readable

CSV

Tabular export

Beta

GraphQL

Query language

New

MCP

For AI agents

Request parameters — GET /v1/fibonaccigenerator

Sent in the query string. Premium parameters are accepted on every plan but only take effect on plans that include them. Anything not listed here is dropped rather than passed through.

Required

Optional

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curl "https://api.apiverve.com/v1/fibonaccigenerator?count=10&startfrom=0" \
  -H "x-api-key: YOUR_API_KEY"

Authentication

Send your key in the x-api-key header. That is the only auth step — no token exchange, and no per-endpoint scope to configure.

Response — GET /v1/fibonaccigenerator

Every APIVerve endpoint returns the same three top-level keys, so one response handler covers your whole integration: status, error and data. Only data changes shape.

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{
  "status": "ok",
  "error": null,
  "data": {
    "sequence": [
      0,
      1,
      1,
      2,
      3,
      5,
      8,
      13,
      21,
      34
    ],
    "count": 10,
    "start_from": 0,
    "first_value": 0,
    "last_value": 34,
    "sum": 88,
    "ratios": [
      1.666667,
      1.6,
      1.625,
      1.615385,
      1.619048
    ],
    "golden_ratio_approximation": 1.619048
  }
}

Response fields

Paths are relative to data. Premium fields are absent rather than zeroed on plans that do not include them, so check for presence instead of comparing to 0.

Response headers

Every response carries your balance, so your own code always knows where it stands without polling anything. All four are exposed to browsers through CORS.

Errors

Read the HTTP status first, then error for the specific reason. The body names the parameter that has to change.

What a call costs — 1 credits per call

Credits are shared across every APIVerve API — one balance, one key, one bill. Failed requests never count against it, so a rejected input costs nothing.

Calls are what the credits buy at this API's rate — spend them here, on any of the other APIs, or across both. Nothing is reserved per endpoint.

Zero-code embed — one snippet, no backend

Drop an interactive Fibonacci Generator form onto any page. The widget calls the API for you, so no key ever appears in your markup and there is nothing to deploy.

Changelog — Fibonacci Generator API

Every change to this endpoint, newest first. Breaking changes ship as a new version and the previous one keeps serving — response fields are added, never removed or retyped in place, so an integration written against v1 keeps working.

Currently v1