isEven (humor) API

Beginner's Pick Science & Math / No Auth Required Beginner HTTPS
Free to Use
80 A
Measured Score 0 50 100 Speed 21/30 Consistency 20/20 Security 20/20 Browser access 15/15 Transparency 4/15 TESTED 2026-09-21

Overview

isEven is a humorous free API that tells you whether a number is even or odd. It is intentionally over-engineered as a joke, turning a one-line math problem into an API call. It is a fantastic first API to practice HTTP requests because it requires no authentication and has the simplest possible input and output.

Beginner Tip

Just append any integer to the endpoint URL and you will get a JSON response immediately with no setup, no API key, and no authentication needed. This is the perfect API to test your first fetch() or curl command.

Measurement Record

What actually happened when we called this API from our own infrastructure. Every value below was recorded by the request, not copied from the provider's documentation.

Request
GET https://api.isevenapi.xyz/api/iseven/42
Result
HTTP 200 · application/json · 71 bytes
Response time
138 ms (median of 3) · fastest 135 ms
Transport
TLSv1.3 · TLS_AES_256_GCM_SHA384 · certificate issued by Let's Encrypt
Browser CORS
Allowed — Access-Control-Allow-Origin: *
Served by
nginx/1.18.0
Answered
8 of 8 weekly checks (100%, since 2026-07-31)
Recorded
2026-09-21

Fields Returned

Top-level fields present in the response we captured, with the type and value we actually received.

Field Type Value received
ad string Buy isEvenCoin, the hottest new cryptocurrency!
iseven boolean true

Captured Response

Captured from a real request to https://api.isevenapi.xyz/api/iseven/42 on 2026-09-21. Long arrays and nested objects are truncated to keep the shape readable.

JSON Response · Captured
{
  "ad": "Buy isEvenCoin, the hottest new cryptocurrency!",
  "iseven": true
}

Field Reference

iseven True if the number is even, false if it is odd.
ad A humorous advertisement shown on the free tier; safe to ignore.

Implementation Example

Calls a real endpoint of this API. Replace any placeholder credentials with your own key.

Request
const url = "https://api.isevenapi.xyz/api/iseven/42";
const response = await fetch(url);
if (!response.ok) throw new Error(`Request failed: ${response.status}`);
const data = await response.json();
console.log(data);

What Can You Build?

Note: These code examples are AI-generated and unverified. Always refer to the official API documentation for accurate usage.

How This API Fails

We deliberately sent this API a broken request and recorded exactly what came back on 2026-09-21. Knowing the shape of an error before you hit it makes error handling much easier to write.

HTTP 404 Requesting a path that does not exist text/html

Returned an HTML error page rather than JSON — worth knowing if your client assumes every response can be parsed as JSON.

Common Errors & Troubleshooting

Generated guidance based on this API's documentation, not observed by us. Treat it as a starting point and check against the provider's own error reference.

400 Bad Request or error in response A non-integer value like a decimal or letter was passed in the URL.
✓ Only pass whole integers in the URL path, e.g., /api/iseven/7.
Unexpected ad field in response The free tier includes an ad field with a promotional message.
✓ Simply ignore or filter out the ad field in your code; only use the iseven boolean field.
CORS error in browser Browser security policy may block requests from certain origins.
✓ Make the call from a Node.js script or backend server to avoid CORS restrictions.

Measured Score Breakdown

Live HTTP request to the API endpoint

Speed 21/30
Consistency 20/20
Security 20/20
Browser access 15/15
Transparency 4/15
Endpoint Response Time 138ms

Fully tested on Sep 21, 2026

Technical Specifications

Auth No Auth
HTTPS REQUIRED
CORS UNKNOWN
Category Science & Math
Difficulty Beginner
Endpoint last called: 2026-09-21

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