Two birth charts in, scored compatibility out.
Salience scoring surfaces the aspects that matter, plus a white-label PDF report in 12 languages. JSON in under 300ms.
The Synastry API pairs well with our other tools. Add
Built for mobile apps and high-volume matching
From ranked inter-aspects to a finished PDF report
Everything you need to add ranked relationship compatibility to your app
The Synastry API compares two birth charts and tells you how the people behind them connect. You send two sets of birth data, and you get back inter-chart aspects, compatibility scores, and the layers most apps never reach: karmic indicators, asteroid synastry, house overlays, temperament matching, and relationship timing. The part developers care about most is salience scoring. Instead of dumping 40 raw aspects on you, the API ranks them so the Venus-Mars connection that drives attraction shows up above the minor stuff. JSON comes back in under 300ms. When you want something a user can keep, one call to the PDF endpoint returns a multi-page, white-label compatibility report in 12 languages.
Synastry compares two birth charts to show how two people interact.
If a single birth chart is a personality profile, synastry is the conversation between two of them.
You POST two sets of birth data (date, time, place) to the synastry endpoint and get JSON back: inter-chart aspects, house overlays, and compatibility scores across several dimensions.
Behind that JSON sit separate engines that each handle one job: aspect-layer scoring weighs each connection, salience scoring ranks which ones matter most, a karmic layer flags Saturn and node contacts, asteroid synastry adds Juno, Ceres, and Vesta, temperament matching compares core styles, and a synthesis layer pulls it all into one read.
Everything returns in under 300ms.
Most compatibility APIs hand you every aspect with equal weight.
A trine between distant points looks the same as a tight Venus-Mars conjunction, so your app has to guess what to show.
Salience scoring fixes that.
It ranks inter-chart aspects by how much they actually shape the relationship, using orb tightness, the planets involved, and chart context.
Your UI can then lead with the three aspects that carry the connection instead of burying them in a list of 40.
For a dating app, that is the difference between 'here is a wall of astrology' and 'here is why you two click.' Salience also makes scores explainable: you can show the user the exact aspects driving their number.
Beyond standard aspects, the API returns layers that usually take a professional astrologer to assemble.
Karmic indicators flag Saturn contacts and lunar node connections that point to long-term, lesson-style bonds.
Asteroid synastry adds Juno (commitment), Ceres (nurturing), and Vesta (devotion) for relationship texture you cannot get from planets alone.
House overlays show where one person's planets land in the other's chart, which reveals the life areas they activate for each other.
Temperament matching compares core styles, and relationship timing surfaces windows when transits make a connection more active.
A synthesis layer ties these into a single plain-language read so you do not have to write interpretation logic yourself.
When a user wants something to keep, send the two charts to POST /api/v3/pdf/synastry-report and get back a multi-page compatibility document.
It covers inter-aspects, the salient connections, house overlays, and the relationship read, formatted as a finished PDF.
The report is white-label, so your brand and styling go on it, not ours, and it generates in 12 languages from the same request.
This turns synastry into a paid feature: apps sell the report as an upgrade, counselors hand it to couples, and content sites offer it as a lead magnet.
One endpoint, no PDF tooling to build on your side.
Basic integration runs about 4 hours; full features take 2-3 days.
Step 1: collect birth data, date and location required, time preferred.
Around 70% of users add birth time once you explain it sharpens the result.
Step 2: POST both profiles to the synastry endpoint and read the JSON, the salience ranking gives you a ready-made order for your UI.
Step 3: decide what to show, a single score, the top-ranked aspects, or the full breakdown.
Step 4: add the PDF endpoint when you want a downloadable report.
Output is plain JSON with no SDK lock-in, so it drops into React Native, Flutter, Swift, or any backend.
Generic APIs return one number and leave interpretation to you.
This one returns ranked aspects you can explain, plus karmic, asteroid, and timing layers a sun-sign API simply does not have.
Speed matters too: a manual synastry write-up takes an astrologer two to three hours, while the API returns the same depth in a single sub-300ms call.
And no other compatibility API ships a white-label PDF report in 12 languages from one endpoint.
You get the data to build live matching and a finished document to sell, from the same place.
Turn swiping into real matches by leading with the salient aspects that explain why two people connect
Hand couples a branded PDF report and save the 2-3 hours a manual synastry write-up takes
Offer karmic, asteroid, and timing layers as premium features without writing interpretation logic
Generate celebrity-couple breakdowns and multilingual PDF reports as lead magnets
| JSON Response Time | <300ms for full synastry analysis |
| Scoring Engines | Aspect-layer, salience, karmic, asteroid, house overlay, temperament, timing, synthesis |
| Salience Scoring | Inter-aspects ranked by relationship impact |
| Asteroid Synastry | Juno, Ceres, Vesta and more added to inter-chart analysis |
| House Overlays | Where each person's planets land in the other's chart |
| PDF Report | POST /api/v3/pdf/synastry-report, white-label, multi-page |
| PDF Languages | 12 languages from a single request |
| Required Birth Data | Date and location required, time preferred, timezones handled automatically |
| Feature | Astrology API | Others |
|---|---|---|
| Aspect Ranking | Salience scoring ranks what matters | Flat list, all aspects equal |
| Depth | Karmic, asteroid, house overlay, timing | Sun-sign or basic aspects |
| Interpretation | Synthesis layer in plain language | Raw data, you build the read |
| PDF Report | White-label, 12 languages, one endpoint | None |
| Output Speed | <300ms JSON | Multiple calls or manual work |
| Price | $37/month for 55K analyses | $99-299/month for less |
Calculate each person's chart before comparing them
Analyze the relationship itself as one chart
Timing for relationship phases and developments
Lighter scoring for simple matching features
Full reference for synastry and PDF endpoints
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