NASA NeoWs (Asteroids) API

Free NASA asteroid API: near-Earth objects by date with size, velocity, miss distance and hazard classification. Works with DEMO_KEY. Tested example.

API key requiredCORS enabledHTTPSFree tier

Endpoint tested and returned HTTP 200 on 20 Aug 2026

What is the NASA NeoWs (Asteroids) API?

NASA's Near Earth Object Web Service (NeoWs) is a free API listing asteroids passing near Earth, with estimated diameter, relative velocity, closest approach distance and whether each is classified as potentially hazardous.

NeoWs draws on NASA's Jet Propulsion Laboratory data, giving you every tracked asteroid making a close approach on a given date, along with its orbital parameters and size estimate.

The `is_potentially_hazardous_asteroid` flag is more nuanced than it sounds. It is a formal classification based on size and minimum orbit intersection distance, not a prediction of impact. Presenting it as 'this asteroid is dangerous' would be badly misleading — the vast majority flagged will never come close to hitting anything.

Quick facts

Base URL: https://api.nasa.gov/neo/rest/v1
Authentication: DEMO_KEY works for testing but is shared and heavily limited. Register a free key at api.nasa.gov.
Rate limit: DEMO_KEY: about 30 requests/hour per IP. Personal key: 1,000/hour.
Pricing: Free. NASA data is public domain.
CORS: Enabled — callable directly from browser JavaScript
Official docs: Read the docs

How to use the NASA NeoWs (Asteroids) API

Every request below was executed against the live API on 20 Aug 2026, and the response shown is the real body it returned — not an illustration.

1. List asteroids approaching on a date

GET https://api.nasa.gov/neo/rest/v1/feed?start_date=2026-08-19&end_date=2026-08-19&api_key=DEMO_KEY

curl

curl 'https://api.nasa.gov/neo/rest/v1/feed?start_date=2026-08-19&end_date=2026-08-19&api_key=DEMO_KEY'

JavaScript (fetch)

const res = await fetch("https://api.nasa.gov/neo/rest/v1/feed?start_date=2026-08-19&end_date=2026-08-19&api_key=DEMO_KEY");
if (!res.ok) throw new Error(`Request failed: ${res.status}`);
const data = await res.json();
console.log(data);

Python (requests)

import requests

res = requests.get("https://api.nasa.gov/neo/rest/v1/feed?start_date=2026-08-19&end_date=2026-08-19&api_key=DEMO_KEY", timeout=20)
res.raise_for_status()
print(res.json())

Response — HTTP 200 (truncated)

{
  "links": {
    "next": "http://api.nasa.gov/neo/rest/v1/feed?start_date=2026-08-20&end_date=2026-08-20&detailed=false&api_key=DEMO_KEY",
    "prev": "http://api.nasa.gov/neo/rest/v1/feed?start_date=2026-08-18&end_date=2026-08-18&detailed=false&api_key=DEMO_KEY",
    "self": "http://api.nasa.gov/neo/rest/v1/feed?start_date=2026-08-19&end_date=2026-08-19&detailed=false&api_key=DEMO_KEY"
  },
  "element_count": 4,
  "near_earth_objects": {
    "2026-08-19": [
      {
        "links": {
          "self": "http://api.nasa.gov/neo/rest/v1/neo/3746623?api_key=DEMO_KEY"
        },
        "id": "3746623",
        "neo_reference_id": "3746623",
        "name": "(2016 EF156)",
        "nasa_jpl_url": "https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=3746623",
        "absolute_magnitude_h": 24.7,
        "estimated_diameter": {
          "kilometers": {
            "estimated_diameter_min": 0.0305179233,
            "estimated_diameter_max": 0.0682401509
          },
          "meters": {
            "estimated_diameter_min": 30.5179232594,
            "estimated_diameter_max": 68.2401509401
          },
          "miles": {
            "estimated_diameter_min": 0.0189629525,
            "estimated_diameter_max": 0.0424024508
          },
          "feet": {
            "estimated_diameter_min": 100.1244233463,
            "estimated_diameter_max": 223.8850168104
          }
        },
        "is_potentially_hazardous_asteroid": false,
        "close_approach_data": [
          {
            "close_approach_date": "2026-08-19",
            "close_approach_date_full": "2026

Parameters

Parameter	Type	Required	Description
`api_key`	string	Required	Your NASA key, or DEMO_KEY. `DEMO_KEY`
`start_date / end_date`	string	Optional	Date range, maximum 7 days apart. `2026-08-19`
`feed`	path	Optional	Browse approaches by date range. `feed`
`neo/<id>`	path	Optional	Full orbital data for one asteroid. `neo/3542519`

Response fields

element_countinteger: Number of asteroids in the response.
near_earth_objectsobject: Keyed by date, each holding an array of asteroids.
...name / idstring: Asteroid designation and NASA identifier.
...estimated_diameterobject: Size estimates in km, m, miles and feet, as min/max ranges.
...is_potentially_hazardous_asteroidboolean: Formal PHA classification — not an impact prediction.
...close_approach_data[].miss_distanceobject: Closest approach in km, miles, lunar distances and AU.
...close_approach_data[].relative_velocityobject: Speed in km/s, km/h and mph.

What you can build with the NASA NeoWs (Asteroids) API

Build an asteroid tracker or space awareness dashboard
Visualise close approaches over time
Create astronomy education resources
Compare asteroid sizes and velocities

Common errors and how to fix them

400 date range too large

start_date and end_date must be within 7 days.

Fix: Page through longer periods a week at a time.

429 OVER_RATE_LIMIT

DEMO_KEY's shared allowance is exhausted.

Fix: Register a free key at api.nasa.gov for 1,000 requests/hour.

Diameter is a range, not a number

Size is estimated from brightness, so it is uncertain.

Fix: Use estimated_diameter_min and _max; never present a single precise figure.

NASA NeoWs (Asteroids) API — frequently asked questions

Is the NASA asteroid API free?

Yes. DEMO_KEY works for testing, and registering a free key at api.nasa.gov raises the limit from about 30 to 1,000 requests per hour.

Does 'potentially hazardous' mean an asteroid will hit Earth?

No. It is a formal classification based on size and how closely the orbit can approach Earth's. It is not an impact prediction, and presenting it as one would be seriously misleading.

Why is the diameter given as a range?

Asteroid size is estimated from brightness and assumed reflectivity, so it carries real uncertainty. Always show the min-max range rather than a single figure.

How far ahead can I query?

The feed endpoint accepts a maximum seven-day range per request, so page through longer periods a week at a time.

Tools that pair with this API

JSON Formatter

Format, beautify and minify JSON online with 2-space, 4-space or tab indentation. Sort keys alphabetically and catch syntax errors instantly — free and private.

Unit Converter

Convert between units of length, weight, temperature, area, volume, speed, time and data storage instantly, with a swap button and common conversion tables.

Alternatives to NASA NeoWs (Asteroids) API

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NASA Exoplanet Archive	Free NASA Exoplanet Archive TAP API with no key: query 5,000+ confirmed exoplanets and their host stars with SQL-like ADQL, returning JSON, CSV or VOTable.	No key	No	21 Aug 2026

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NASA NeoWs (Asteroids) is an independent third-party service and is not affiliated with ByteTools or ByteVancer. Details on this page were verified on 20 Aug 2026; always check the official documentation before relying on this API in production, as terms and limits can change.