OnWater API
Overview
OnWater is a simple free API that tells you whether a given latitude and longitude coordinate is on water or on land. You pass coordinates and get back a boolean answer — perfect for validating location data or building map-based games. No API key is needed, making it extremely easy to use right away.
Beginner Tip
This API answers one simple question: is this point on water? Use it to validate that users are not accidentally placing markers in the ocean. Latitude ranges from -90 to 90 and longitude from -180 to 180.
Available Data
Example Response
{
"status": "success",
"data": {
"result": "Data from OnWater",
"description": "Determine if a lat/lon is on water or land",
"timestamp": "2025-01-15T10:00:00Z"
}
} Field Reference
lat The latitude value you submitted in the request lon The longitude value you submitted in the request water True if the coordinate is on water; false if it is on land Implementation Example
const url = "https://onwater.io/";
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.
Common Errors & Troubleshooting
Matrix Score Breakdown
Fully tested on Apr 5, 2026
Technical Specifications
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