What is Synastry?
Synastry is the astrological technique of comparing two natal charts to assess relationship compatibility. It's the foundation of astrology-based matching in dating apps like Co-Star, The Pattern, and Hinge's astrology feature.
Instead of just matching sun signs ("You're both Leos - great match!"), synastry analyzes how every planet in one chart interacts with every planet in the other. This gives a nuanced compatibility picture.
Key Synastry Aspects
| Aspect Comparison | What It Shows |
|---|---|
| Venus-Mars | Physical attraction, chemistry |
| Moon-Moon | Emotional compatibility, comfort |
| Sun-Moon | Core personality + emotions fit |
| Mercury-Mercury | Communication style match |
| Saturn aspects | Long-term stability, commitment |
Quick Start: Calculate Compatibility
Python
import requests
compatibility = requests.post(
"https://api.vedika.io/v1/query",
headers={"Authorization": "Bearer YOUR_API_KEY"},
json={
"query": """
Calculate synastry compatibility between:
Person A: Born March 15, 1992, 2:30 PM, New York
Person B: Born July 22, 1990, 10:15 AM, Los Angeles
Include compatibility score, strongest aspects,
and potential challenges.
""",
"system": "western"
}
).json()
print(f"Compatibility: {compatibility['score']}%")
print(f"Strongest: {compatibility['strongest_aspects']}")
print(f"Challenges: {compatibility['challenges']}")Example Response
{
"score": 78,
"rating": "High Compatibility",
"strongest_aspects": [
{
"aspect": "Venus trine Mars",
"orb": 2.3,
"meaning": "Strong physical attraction and romantic chemistry"
},
{
"aspect": "Moon conjunct Venus",
"orb": 1.8,
"meaning": "Deep emotional connection and nurturing"
}
],
"challenges": [
{
"aspect": "Sun square Saturn",
"orb": 3.1,
"meaning": "May feel restricted or criticized by partner"
}
],
"summary": "This relationship has strong romantic potential with excellent Venus-Mars chemistry. The emotional bond (Moon-Venus) provides stability. Watch for control dynamics with Sun-Saturn."
}Implementing in a Dating App
Here's how to add synastry-based compatibility to your dating app:
JavaScript / React
async function getCompatibility(userA, userB) {
const response = await fetch("https://api.vedika.io/v1/query", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.VEDIKA_API_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
query: `Calculate synastry between:
Person A: Born ${userA.birthDate} at ${userA.birthTime} in ${userA.birthPlace}
Person B: Born ${userB.birthDate} at ${userB.birthTime} in ${userB.birthPlace}
Return compatibility score and top 3 aspects.`,
system: "western"
})
});
return response.json();
}
// Usage in match card component
function MatchCard({ match, currentUser }) {
const [compatibility, setCompatibility] = useState(null);
useEffect(() => {
getCompatibility(currentUser, match).then(setCompatibility);
}, [match]);
return (
<div className="match-card">
<img src={match.photo} alt={match.name} />
<h3>{match.name}</h3>
{compatibility && (
<div className="compatibility-badge">
♡ {compatibility.score}% Compatible
</div>
)}
</div>
);
}Best Practices for Dating Apps
- Don't gate on low scores - Show compatibility as a fun feature, not a blocker
- Cache results - Compatibility doesn't change, cache indefinitely
- Require birth time for accuracy - Without birth time, rising sign is unknown
- Use it for engagement - "See why you're 85% compatible" drives conversations