How Geneacta works
The site’s user guide — above all its way of counting: a tree’s two anchors, the Geneacta numbering and the classic numbering (Sosa and d’Aboville).
The site in a nutshell
Geneacta brings together your tree, community-indexed records and mutual help. Your data is yours: export it at any time in the open .genea format (and GEDCOM), and nothing an import cannot translate is ever lost — everything is kept and reported.
Nothing is ever overwritten: every piece of information is a dated assertion that can be invalidated but not rewritten. That is what makes it possible to step back and understand where each datum comes from.
The tree, profiles, the graph
Every person has a full profile: recorded names, sourced events, family, images, and a work plan (compare, my leads, recent activity). The graph handles like a map: grab the background to move, Ctrl + wheel to zoom, click a card to recentre — no page reload.
The ⤓ button on a card opens that person in a bottom panel, to compare two individuals side by side — the gesture you make constantly between two namesakes.
The two anchors: subject and founder
A tree has TWO viewpoints, not one. The subject (🌸) is the person the lineages start from — often you, or a child of today. The founder (🪵) is the founding ancestor the tree is built on. They need not coincide.
Each person therefore carries TWO numbers, one against each anchor, shown as plates on their profile and on their card in the graph. These numbers are computed, never stored: move an anchor (profile icons, top right) and the whole numbering follows.
🌸 subject — green plate on the profile 🪵 founder — purple plate on the profile
Geneacta numbering (the default)
A dotted path, read left to right. The first digit gives the direction: 1 opens an ascent (from the subject), 0 opens a descent (from the founder). Each following number is a rank: 1.3.2 reads “2nd parent of the 3rd parent of the subject”.
It is permissive by construction: 1, 2 or N parents, same-sex parents, blended families — every parent has a rank, nobody is left without a number.
- 1
- the subject
- 1.3.2
- 2nd parent of the subject’s 3rd parent
- 0
- the founder
- 0.2.1
- 1st child of the founder’s 2nd child
Classic numbering (Sosa and d’Aboville)
The system genealogists have used for a century, applied STRICTLY. Ascending (Sosa-Stradonitz): the subject is 1; the even number (2n) goes to the first man of the couple — or to another parent if there is no man; the odd number (2n+1) to the first woman — or another if there is no woman. A single parent carries one number only, that of their line.
The system is binary by definition: beyond two parents, the others get no Sosa number. We do not bend the rule — if your family cannot be read in it, the Geneacta numbering is made for it, selectable per tree in “My trees”.
Descending from the founder: d’Aboville. The founder is 1, their children 1.1, 1.2… in birth order, and so on.
- 1
- the subject (Sosa 1)
- 2 · 3
- their father (2) and mother (3) — even to the first man, odd to the first woman
- 6
- the mother’s father (3 × 2): a father’s number is always double his child’s
- 1.2.1
- 1st child of the founder’s 2nd child (d’Aboville)
Evidence, conclusion, hypotheses
When sources disagree (two birth dates, two possible ancestries), Geneacta does not choose for you: alternatives are kept in bundles, and you read the tree THROUGH a hypothesis, switchable in one click on the profile.
Search
Search ignores accents and word order: “lefevre joseph” finds “Joseph LEFÈVRE”. The Search tab queries, as you choose, your trees, one specific tree, trees published by other members, and indexed records.
Privacy: people with no known death NEVER enter the public index — neither yours nor anyone else’s. Publishing a tree is an explicit, reversible choice, and unpublishing erases everything that had been projected.
Automatic hints
In the background, the system compares your tree with published trees and indexed records: same surname and given name, close years. It never changes anything — it suggests, you keep or dismiss, and a dismissed hint does not come back.
Nothing gets lost
Whatever a GEDCOM, GeneWeb or Gramps import cannot translate is kept as is, linked to the person concerned, and visible on their profile (“Everything we know”). Whatever an export cannot write is counted and reported. You can leave at any time with all of your data.