Offline-first bespoke data collection apps from Open Data Ensemble
About this app
Formulus is the mobile data collection client of the Open Data Ensemble (ODE) platform.
It allows organizations, research teams, and public sector institutions to build their own bespoke data collection applications based on structured forms defined using the JSONForms specification.
Forms and application logic are defined externally, meaning the same Formulus app can host many different data collection projects without requiring app updates.
Key features include:
• Flexible form-based data collection using JSONForms • Offline-first operation for use in the field • Secure bi-directional synchronization with an ODE Synkronus server • Support for complex data structures and validation • Designed for long-term maintainability and open standards
Formulus is particularly suited for environments where reliable data collection is needed under challenging conditions, such as:
• field research • public health surveillance • environmental monitoring • humanitarian and development projects • decentralized data collection initiatives
The app requires access to an ODE Synkronus server for synchronization and project management. Organizations typically run their own Synkronus server to host forms, manage users, and collect submitted data.
If you do not yet have access to a Synkronus server but would like to explore the application, a public demonstration environment may be available. See the project website for details.
Formulus is part of the Open Data Ensemble ecosystem, an open-source initiative focused on building interoperable tools for decentralized, standards-based data collection.
Source code and documentation: https://opendataensemble.org
Licensed under MIT, by Open Data Ensemble.
What's New in v1.0.1
Imported from the F-Droid repository index.
Version history
Jun 22, 2026 · 33.7 MB · Android API 24–36 · code 5
Imported from the F-Droid repository index.
SHA-256 28b8ad73010f1943b758812618592d73637d1946f4c7e5c18b5de3e8b9a4aca7
Jun 22, 2026 · 34.3 MB · Android API 24–36 · code 4
Imported from the F-Droid repository index.
SHA-256 ed53ee727f657ebd3f231c83193d1ffc36582fdf67abbac767e0bb6a02373095
Jun 22, 2026 · 33.2 MB · Android API 24–36 · code 3
Imported from the F-Droid repository index.
SHA-256 658a5e60cf141e6cbbc1ef846861daf66f0337e6c0e4a7d759bdfbb997ad740f
Will it run on your device?
92%
- Runs on a broad range of modern Android versions.
- Multiple CPU architectures are covered.
- Aligned with the latest Android target SDK expectations.
Installation Guide
Open Settings on your Android device
Go to Security → Unknown sources (or Install unknown apps)
Enable "Allow from this source" for your browser or file manager
Open the downloaded APK file from your Downloads folder
Tap "Install" and wait for installation to complete
Launch the app from your home screen
Make sure to re-enable Unknown Sources restrictions after installation for security.
How to install this safely
How to verify the file you downloaded
Before you install anything, confirm the file is the one described here. On a computer, run shasum -a 256 your-download.apk (macOS or Linux) or certutil -hashfile your-download.apk SHA256 (Windows), then compare the output character-for-character with the SHA-256 on this page. If a single character differs, the file is not the build we recorded — delete it.
What the signing certificate proves
Every Android app is signed with a private key that only its developer holds. The fingerprint on this page is a hash of the matching public certificate, and it proves continuity rather than identity: it tells you a build came from whoever signed the earlier ones. Android enforces this at install time — if a package claiming to be org.opendataensemble.formulus is signed with a different key, the system will refuse to install it over your existing copy. A fingerprint that changes between releases is worth pausing on, because a repackaged app that has been modified by someone else cannot keep the original signature.
How to roll back to an earlier version
If the current release misbehaves, 1.0.1 is the last build before it. Android will not install an older version code over a newer one, so you must uninstall Formulus first — which clears its local data unless you have a backup. Reinstall the older APK only if its signing fingerprint matches the build you already trust, and check the API range: an older release may target an Android version your device has moved past.
Why we list sources instead of hosting everything
The official store channel is almost always the right choice: it updates automatically and carries the publisher's own distribution guarantees. A direct APK is useful when a device has no store access, when a rollout has not reached your region, or when you need a specific version — and only when the publisher has authorized that copy. APKBrowse does not list pirated, cracked, or unauthorized rebuilds of Formulus, and a listing is removed when the evidence for it stops holding up.
Get Formulus
Every source we list for org.opendataensemble.formulus is legality-reviewed. Pirated or cracked builds are never offered.
Other sources
F-Droid listing
officialF-Droid builds this app from source and signs it. This is its official listing, with older builds and full release notes.
Source code
verified publisherThe upstream repository this build is compiled from.
We check legality and signature continuity, but device behaviour still varies. Install at your own discretion.
App Information
Security Verification
We record provenance; we do not run malware scans. Verify the hash yourself before installing.
SHA-256 Hash
28b8ad73010f1943b758812618592d73637d1946f4c7e5c18b5de3e8b9a4aca7
Signing certificate
7765daaf9659e3e95f63a3fdf7ff79d3684140586853e2f0d16c59a353f4a3aa
Permissions Required
Previous Versions
The signing certificate fingerprint for this release is on record, so a build that does not match it did not come from this publisher.
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