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Building Custom Apps

A custom_app is a zipped archive containing two folders:

custom_app.zip
├── forms/          # Questionnaires (JSONForms specifications)
└── app/            # Application layer (HTML/JavaScript)

What is a custom_app?

In ODE, forms alone are just questionnaires. But custom_apps turn them into rich, interactive data collection experiences. You can:

  • Look up existing observations (filled-out form responses)
  • Display dashboards and summaries of collected data
  • Open follow-up forms with pre-populated values
  • Build longitudinal workflows (registration → follow-ups)
  • Add helper text, validation, and guidance for data collectors

The app layer is built with HTML and JavaScript — if you can build a web page, you can build a custom_app. Support for frameworks like React, SolidJS, Angular is fully supported.

When to use custom apps

Use custom_apps when you need:

  • Longitudinal data collection — follow-up questionnaires linked to initial registrations
  • Context-aware forms — show relevant forms based on previous answers
  • Dashboards — visualize or summarize collected data in real-time
  • Offline support — access and display data on field devices
  • Smart workflows — complex data collection journeys beyond simple forms

Key concepts

Forms vs. Observations

  • Form — The specification (schema.json + ui.json) that defines what data to collect
  • Observation — A single filled-out instance of a form (the actual data)

JSONForms

Custom apps use JSONForms extended with ODE-specific question types:

  • Standard types: text, number, date, dropdown, radio, checkbox
  • ODE extensions: photo, GPS, QR code, signature, and more

Data relationships

In longitudinal workflows, observations are linked:

  • One-to-many: One registered entity → many follow-up observations
    • Example: One coffee bean registration → multiple shots pulled

Getting started

Ready to build your first custom_app? See the step-by-step guides:

Example: Coffee Tracker

Throughout these guides, we'll build Coffee Tracker — a simple but complete app for collecting information about roasted coffee beans and tracking espresso shots.

Version 1.0: Basic registration form for coffee beans (forms + static landing page)
Version 2.0: Add longitudinal tracking of shots pulled, dashboards, and data injection

Upload to Synkronus

Once built, upload via:

  • Web UI — Synkronus Portal → App Bundle page
  • CLI — synk app-bundle upload path/to/app.zip -a

Then users sync by opening Formulus → Sync page → Update App Bundle.

Next steps

  1. Follow the v1 guide for a complete walkthrough
  2. Extend with v2 guide for longitudinal features
  3. Check the Reference → App Bundle Format for technical details

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