Janus and Astrolium are not the same shape of tool. Janus is a Windows desktop application from Astrology House in New Zealand, sold once for US$275, built around the source-text logic of William Lilly and the Olivia Barclay school. Astrolium is a web product whose horary engine runs the Lilly-school judgment itself — radicality scored, significators selected by question category, translation and collection of light flagged, and a yes/no verdict with confidence and reasoning returned per cast.
What Janus is
Astrology House has shipped Janus since the late 1990s. Sue Ward called the horary module "the best I've seen." Robert Zoller endorsed it as "the most accurate, authentic and easy to use Medieval Astrology software available." John Frawley wrote that it "undercuts programs which offer a mere fraction of its variety, but is significantly cheaper than its obvious rivals." That endorsement set held for two decades and made Janus the practitioner standard for traditional horary on the desktop.
The current build is Janus 6.4. Pricing on the Astrology House store: US$275 for a full licence, US$99 upgrade from Janus 5 to 6. There is a Light version for beginners and a 30-day free trial of the full product. Distribution is Windows-only — Mac users run it through Parallels, Boot Camp, or a VM. The software functions, in the publisher's own words, as a Windows program.
Where Janus still leads
Source-text depth. The Traditional and Medieval modules carry features rarely found elsewhere: primary directions with Egyptian Terms and House Cusps directing, decennials with hourly periods, zodiacal releasing with Arabic Part theme selection, almutens of houses, the Male Part of Marriage, professional significators by trade. For students working through Frawley, Zoller, or Sue Ward course material, Janus shows the same data the course shows.
One-time licence. US$275 once, no expiry, no subscription. For a practitioner casting two horaries a week for a decade, the cost per cast is tiny.
Offline. Once installed, Janus runs without a network. That matters for in-person consultations in places with weak internet, and for practitioners who simply prefer their tools not phoning home.
The chart, not the verdict. Janus surfaces every traditional data point — hour ruler, ASC degree, Moon's via combusta status, lunar mansion, dispositor wheels — and lets the astrologer judge. For practitioners who view automated judgment as a category error, that is the right design.
Where Astrolium leads
Automated radicality. Astrolium's /v3/horary/analyze endpoint scores radicality from 0 to 100 and checks all eight standard considerations: late Ascendant, early Ascendant, Saturn in the 7th, Moon void of course, Moon in via combusta, malefic on the Ascendant, hour-ruler / ASC-ruler mismatch, and Moon at 29°. Each present consideration is flagged by severity and shown with an explanation. The recommendation comes back as proceed, caution, or decline.
Significators picked for you. The engine reads the question, identifies the category (job, love, lost objects, lawsuit, illness, travel, property, money, marriage, pregnancy, or general — each with subcategories), assigns querent and quesited, and adds a natural significator where the tradition calls for one. Full dignity_info comes back on each: sign, essential dignity, dignity score, accidental conditions, domicile ruler, exaltation ruler.
Perfection logic, including the secondary mechanics. Mutual reception and one-way reception are detected and described. Translation of light returns the translator planet, the separation aspect, the application aspect, the perfection orb, and a reasoning note. Collection of light returns the collector and both significators' degrees to perfection. The reader sees the mechanic called out, not just the aspects.
An explicit judgment. The judgment object returns yes, no, or unclear, plus a confidence percentage, a testimony score split positive / negative / neutral, the key factors that drove the call, and a full reasoning paragraph. The practitioner is free to override; the engine has done the bookkeeping.
Fertility as a first-class question. /v3/horary/fertility-analysis is a separate endpoint. It composites sign-fertility weights for Moon, 5th cusp, L5, Jupiter, and Ascendant; runs L1→L5 and Moon→L5 testimony; calculates the Arabic Parts of Children and Pregnancy; returns a fertility score 0–100; and emits timing windows with confidence levels. Janus, like Solar Fire and Astro Gold, has no equivalent specialist mode.
Modern workflow. Sub-300ms chart render on mobile data. Live client links that open in any browser without an install. A client CRM that stores casts with session notes. Free tier covers 25 clients across all 58 calculators; paid tier is US$29/mo.
When you'd use both
Many traditional practitioners are landing on a split workflow. Janus stays on the desktop for offline work, for teaching from screens the curriculum is built around, and for the practitioner's own judgment work where automated yes/no would feel out of place. Astrolium picks up the client-facing surface: every cast logged against a client, the radicality and perfection logic running as a second opinion, the fertility analyser when the question calls for it, and a shareable link the client opens on their phone.
If you already own a Janus 5 licence, the US$99 upgrade to Janus 6 keeps your desktop tool current. Astrolium's free tier is enough room to test the engine against twenty-five real casts before deciding whether to add the paid plan.
For broader comparisons, see Solar Fire vs Astrolium, Astro Gold vs Astrolium, and the best astrology software 2026 roundup. For Astrolium pricing details, see pricing.