Synastry & Compatibility API

Full set of endpoints for compatibility analysis - from classical synastry to group matrices of up to 10 people.

What’s calculated

Cross-aspects: aspects between planets of two charts (Sun-Venus trine, Moon-Mars square, etc.)
Compatibility score: 0–100 numeric score with label (harmonious, balanced, mixed, challenging)
Harmony/Tension: weighted sums of harmonious and tense aspects
Composite chart: midpoints between planets of two people
Davison chart: chart for the mean date and coordinates
Group matrix: pairwise compatibility for each pair (2–10 people)

The same computation with an interface around it: synastry in the AstroWay app. Useful when the result has to be shown to somebody who does not read JSON.

Endpoints

Endpoint	Credits	What it returns
`/v1/synastry`	50	Cross-aspects + compatibility score
`/v1/composite`	50	Composite chart (midpoints)
`/v1/davison`	50	Davison chart (mean date)
`/v1/coalescent`	50	Coalescent chart
`/v1/group-synastry`	100	Compatibility matrix for 2–10 people
`/v1/human-design/compatibility`	100	HD compatibility

Example

curl -X POST https://api.astroway.info/v1/synastry \
  -H "X-Api-Key: aw_live_your_key_here" \
  -H "Content-Type: application/json" \
  -d '{
    "chart1": {
      "date": "1990-07-14", "time": "14:30:00",
      "timezoneOffset": 3, "latitude": 50.45, "longitude": 30.52
    },
    "chart2": {
      "date": "1992-03-22", "time": "09:15:00",
      "timezoneOffset": 2, "latitude": 48.85, "longitude": 2.35
    }
  }'

const r = await fetch('https://api.astroway.info/v1/synastry', {
  method: 'POST',
  headers: {
    'X-Api-Key': process.env.ASTROWAY_API_KEY!,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    chart1: { date: '1990-07-14', time: '14:30:00', timezoneOffset: 3, latitude: 50.45, longitude: 30.52 },
    chart2: { date: '1992-03-22', time: '09:15:00', timezoneOffset: 2, latitude: 48.85, longitude: 2.35 },
  }),
});
const { data: result } = await r.json();

console.log(`Score: ${result.compatibility.score}/100`);
console.log(`Label: ${result.compatibility.label}`);

import os, requests

r = requests.post(
    'https://api.astroway.info/v1/synastry',
    headers={'X-Api-Key': os.environ['ASTROWAY_API_KEY'], 'Content-Type': 'application/json'},
    json={
        'chart1': {'date': '1990-07-14', 'time': '14:30:00', 'timezoneOffset': 3, 'latitude': 50.45, 'longitude': 30.52},
        'chart2': {'date': '1992-03-22', 'time': '09:15:00', 'timezoneOffset': 2, 'latitude': 48.85, 'longitude': 2.35},
    },
)
result = r.json()['data']
print(f"Score: {result['compatibility']['score']}/100 ({result['compatibility']['label']})")

<?php
use GuzzleHttp\Client;

$aw = new Client(['base_uri' => 'https://api.astroway.info/v1/']);
$r = $aw->post('synastry', [
    'headers' => ['X-Api-Key' => getenv('ASTROWAY_API_KEY')],
    'json' => [
        'chart1' => ['date' => '1990-07-14', 'time' => '14:30:00', 'timezoneOffset' => 3, 'latitude' => 50.45, 'longitude' => 30.52],
        'chart2' => ['date' => '1992-03-22', 'time' => '09:15:00', 'timezoneOffset' => 2, 'latitude' => 48.85, 'longitude' => 2.35],
    ],
]);
$result = json_decode($r->getBody(), true)['data'];
echo "Score: {$result['compatibility']['score']}/100 ({$result['compatibility']['label']})\n";

Example response (compatibility)

{
  "compatibility": {
    "score": 51,
    "label": "mixed",
    "harmony": 15.8,
    "tension": 16.8,
    "top": [
      { "aspect": { "planet1": "Venus", "planet2": "Moon", "type": { "name": "Square", "angle": 90 } }, "strength": 2.09, "sign": -1 }
    ]
  }
}

Use cases

Dating apps

Call /v1/synastry on match - compatibility score as an additional ranking factor. Cache the result for the pair (immutable input = immutable output).