Kerykeion is an astrology ecosystem that includes an open-source Python library, professional astrology software, a hosted API and a large collection of free educational guides.

Where should beginners start?

Start with the Foundations learning path, then move through planets, signs, houses and aspects before combining them in a complete birth-chart reading.

What is Astrologer Studio?

Astrologer Studio is a professional workspace for creating charts, organising clients and subjects, studying relationships and predictive cycles, and producing reports.

What is the difference between the Kerykeion Library and the Astrologer API?

The Library is an open-source Python package that developers run directly. Astrologer API provides hosted access from any programming language without managing the calculation infrastructure.

Can I calculate my birth chart for free?

Yes. The free birth-chart tool lets you generate a personal chart and use it as a starting point for exploring the educational library.

Is Kerykeion open source?

The core calculation library and related developer tools are open source and available for inspection and contribution.

Data Driven
Astrology 💫

Open-source Python library, cloud astrology software, hosted Astrology API, and 10,902+ free guides. Built on NASA JPL ephemerides and downloaded over 2 million times.

Browse Astrology Guides Free Birth Chart

For professionals: Astrologer StudioFor developers: Read the Docs · Hosted API

Try Astrologer API

Use Astrologer API to add natal charts, synastry, transits, and AI context to your app. No Python required.
Subscribing helps support the project and keeps it growing!

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The open standard

The engine the world builds astrology on.

Downloaded more than two million times, Kerykeion powers research projects, commercial products, professional software and indie apps across the world. One open engine, free for anyone to read, fork and rely on.

2M+Downloads from PyPI

2,800+Developers on the Astrologer API

63Celestial points per chart

100%Open source, under AGPL-3.0

Explore the Library View on GitHub

Explore astrology

Build a deeper understanding of the birth chart.

Start with the foundations or explore relationships, timing techniques, traditional methods and specialised branches through thousands of connected guides.

Browse All Guides Start with the Foundations

Start here

Foundations

The building blocks: planets, signs, houses and aspects.

363 guides

Core

Birth Charts

Understand the chart as a complete symbolic system.

6,081 guides

Relationships

Synastry

Explore the dynamics between two charts.

624 guides

Relationships

Composite Charts

The chart of the relationship itself.

510 guides

Forecasting

Transits

Follow current planetary movements and cycles.

467 guides

Forecasting

Planetary Returns

Solar, lunar, Saturn, Jupiter and Chiron returns.

445 guides

Advanced study

Predictive Techniques

Progressions, directions and timing methods.

346 guides

Tradition

Traditional Techniques

Classical frameworks, dignities and interpretative methods.

507 guides

Specialised

Specialized Branches

Sabian symbols, astrocartography, harmonics and midpoints.

1,046 guides

New to astrology?

Start with a structured learning path.

Move from isolated meanings to a coherent understanding of the chart.

Beginner

Learn the planets, signs, houses and aspects before combining them into a complete chart interpretation.

Start the Beginner Path

Intermediate

Move into chart rulers, aspect patterns, synastry, composites and current transits.

Continue Your Study

Advanced

Explore predictive techniques, traditional frameworks and specialised branches.

Explore Advanced Astrology

The sky right now

Follow current planetary movements in context.

Track planetary positions, retrogrades and lunar phases, then open the guides that explain their astrological meaning.

Planet	Position	Sign	Speed	Declination








Name Phase Day

Explore Transits See Transits in Your Chart

Astrologer Studio workspace showing Albert Einstein's natal chart with birth data and natal points

Professional astrology software

A complete workspace for professional astrological practice.

Create and compare charts, organise clients and subjects, study relationships and predictive cycles, and prepare clear professional reports from one browser-based workspace.

Client workKeep subjects, notes and chart histories organised in one place.

Relationship analysisWork with synastry, composite charts and multi-chart comparison.

ForecastingExplore transits, returns, progressions, solar arcs and other timing techniques.

Professional outputsCreate chart visuals and reports ready to share with clients.

Start Your Free Trial Create a Free Birth Chart

3-day free trial · No credit card required

Open-source Python astrology library

The calculation engine behind the Kerykeion ecosystem.

Build reliable astrology applications with transparent calculations, structured data models, configurable analysis and professional SVG charts.

CalculatePlanets, houses, aspects, returns and ephemeris data.

AnalyseChart relationships, patterns and distributions.

RenderNatal, synastry, transit and return charts as SVG.

IntegrateTyped models, structured JSON and AI-ready context.

Read the Documentation Explore the Library View on GitHub

pip install kerykeion

from kerykeion import AstrologicalSubjectFactory
from kerykeion.chart_data_factory import ChartDataFactory

subject = AstrologicalSubjectFactory.from_birth_data(
    "John Doe",
    1990, 7, 15, 10, 30,
    lng=12.4964,
    lat=41.9028,
    tz_str="Europe/Rome",
    online=False,
)

chart_data = ChartDataFactory.create_natal_chart_data(subject)

Chart rendering

Every chart type, six themes, nine languages.

Natal, synastry, transit, composite and return charts. Wheels, aspect grids and data tables, rendered as scalable SVG straight from the library.

Natal chart with wheel, aspect grid and data table

Natal chartModern

Natal chart rendered with the dark theme

Natal chartModern · Dark

Natal chart rendered with the strawberry theme

Natal chartModern · Strawberry

Synastry chart comparing two charts, with aspect table

SynastryModern

TransitsModern

Composite chart rendered with the modern theme

CompositeModern

Solar return chart with return and natal wheels

Solar ReturnModern

Explore related symbolic traditions

Beyond the birth chart.

Learn Tarot

Study all 78 cards and the systems behind them.

Explore the Major and Minor Arcana, spreads, symbolism, historical traditions and practical methods of interpretation.

Explore Tarot

Learn Crystals

Discover stones, traditions and correspondences.

Browse crystal profiles, mineral families, practical guides and their astrological and symbolic associations.

Explore Crystals

Built in the open

Transparent calculations. Open technology.

The engine that computes every chart on this site is open source, and has been since 2020. You can read the code, check the maths and run it yourself. Astrologer Studio and the Astrologer API are what pay for that work to continue.

About Kerykeion Open-Source Projects

Precise by default

Positions come from NASA JPL ephemerides and are checked against a test suite on every release, not rounded off or copied from a table.

Nothing hidden

Read the source and see exactly how a house cusp, an aspect or a return is calculated. No black boxes, no proprietary maths.

Here for the long run

Kerykeion has been maintained since 2020 and runs in production apps, research projects and every page of this site.

Yours to keep

Released under AGPL-3.0. Fork it, audit it, or self-host it. The engine never stops being yours to inspect.

Frequently asked questions

Questions about the Kerykeion ecosystem.

One engine. Every way to work with the sky.

Read a guide, calculate a chart, or build with the API. It all runs on the same high-precision, open-source engine.

Browse Astrology Guides Subscribe to the API

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