Family tree application that runs entirely in your browser. No server required, your data stays with you.
Online version: stromapp.info
People & Records
- Add, edit, delete persons; multiple marriages, divorces, step-siblings
- Adoptive, step and foster parent-child relationships (drawn distinctly)
- Flexible dates ("around 1880", "before 1900", year only)
- Photos, life events (baptism, occupation, residence…), notes
- Sources & citations with a per-tree catalog; document attachments (scans, PDFs)
- Duplicate hints while typing; family wizard (add a whole family in one form)
- Undo/redo for every change
Visualization
- Interactive tree with generation rows; zoom (scroll/pinch) and pan (drag/swipe)
- Family, descendants-only and timeline view modes
- Overview minimap for large trees; advanced search filters with in-tree highlighting
- Relationship calculator ("second cousin once removed")
- Family statistics charts; anniversaries panel and "on this day" reminders
- Responsive design (desktop, tablet, mobile — long-press action sheet on touch)
- Light/dark theme
Family Collaboration (no cloud)
- "Send to a relative": e-mail a single file with a personal note
- The recipient opens it, fills in their branch, and sends it back with one click
- Strom recognises the returned file and offers a side-by-side merge
Tree Management
- Multiple trees in one app; rename, duplicate, delete
- Smart merge with conflict resolution; validation; statistics
- Automatic versioned backups with one-click restore (time capsules)
- Person and tree locking
Import / Export / Print
- GEDCOM import & export (Ancestry, FamilySearch, Gramps; events, sources, PEDI)
- JSON export/import; HTML file import; branch-only export
- Standalone HTML file export (the whole app + data, works offline)
- Printable family book (chapters, sources as footnotes, person index)
- Poster export (SVG / PNG / tiled print)
- Living-person privacy filter for every export (initials / anonymous / minimal)
Privacy & Offline
- No server, no accounts, no tracking — data stays in your browser
- Optional AES-256 encryption; password-protected exports
- Installable PWA with full offline mode
Two Ways to Use
| Online Version | Standalone File |
|---|---|
| stromapp.info | Download strom.html |
| PWA - install to home screen | Works offline, no internet needed |
| Data in browser storage | Data in browser storage (separate) |
| Always latest version | Version frozen at download time |
Note: Online and standalone versions use separate storage. To transfer data between them, use JSON export/import or import the HTML file directly.
Other
- Person search (live search + URL parameter)
- English and Czech language
- Offline support (PWA)
Visit stromapp.info and start adding your family.
Download strom.html from Releases and open in any browser.
git clone https://github.com/ACiDekCZ/strom.git
cd strom
npm install
npm run build
# Output: strom.html- Add Person - Click "+ Add Person" or use the button on empty state
- Edit Person - Click on any person card to edit details or manage relationships
- Navigate - Drag to pan, scroll to zoom, or use zoom controls
- Focus - Click person → "Focus" to see only their immediate family
- Export - Menu → "Export App" to save your tree as portable HTML file
- Import - Supports JSON, GEDCOM, and Strom HTML files
- TypeScript with strict mode
- esbuild for bundling
- No runtime dependencies
- Single HTML file output (~550kb)
- Works offline in any modern browser
- Progressive Web App (PWA) support
npm run watch # Dev mode with auto-rebuild
npm run build # Production build
npm run typecheck # Type checking
npm test # Run testsCopyright © 2026 Milan Víšek.
This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License along with this program. If not, see https://www.gnu.org/licenses/. See LICENSE.
The source code of the running app (https://stromapp.info/run/) is at https://github.com/ACiDekCZ/strom; the app links to it in its About dialog.
"Strom" is the name of the original project (https://stromapp.info); please give a modified version a name of its own.
These keep their own licenses; their notices and license texts are also
embedded in the app's HTML (a comment in <head>):
- Strom Serif font: a modified (subsetted) version of Source Serif 4, renamed as its Reserved Font Name requires. Source Serif 4: Copyright 2014 - 2021 Adobe Systems Incorporated, with Reserved Font Name "Source"; SIL Open Font License 1.1.
- Instrument Sans font: Copyright 2022 The Instrument Sans Project Authors; SIL Open Font License 1.1.
- Some interface icons come from or are based on Lucide (ISC License, Copyright (c) Lucide Icons and Contributors) and Feather (MIT License, Copyright (c) 2013-2023 Cole Bemis).
- Map tiles are loaded at run time from OpenStreetMap (© OpenStreetMap contributors, https://www.openstreetmap.org/copyright); the map shows this attribution.
Authors: Milan Víšek and Claude (Anthropic)
Strom - Your family history, always with you.