A disc golf bag tracker that belongs to you — your discs, your data, on your own device.
No accounts. No cloud. No tracking. No ads.
Disc Tracker is two things that share one brain:
- A local-first Android app — now the primary, canonical build. Started as a port, has since grown past the website (Score tab, Disc Suggest's swipe-to-learn engine, full backup/restore, the larger Try Discs catalog) and is where new features land first.
- A self-hosted web app — the original, running on a small personal VPS. Still maintained, but secondary — a simpler surface that isn't required to mirror everything the app does.
Both share the same 1,660-disc library, the same flight-arc math, and the same core idea: a fast, private place to manage your bag, understand how your discs fly, and figure out what to throw. The mobile app also offers an optional, larger catalog as an in-app download — disc data by Try Discs, used only for on-device lookup/suggest/audit, never re-served or published as a standalone dataset. Try Discs lists 2,147 molds; the downloaded catalog includes 1,874 of them — the other 273 are left out because they're missing complete flight numbers (speed/glide/turn/fade), which this app requires so every disc works fully in Flight Shaper and Disc Suggest.
This is the whole point, so it goes first.
- No accounts, no passwords, no sign-up. You just use it.
- No cloud. The web app stores everything in a local SQLite file on the machine you run it on. The Android app stores everything in a SQLite database on your phone. There is no backend service collecting anything.
- No analytics, no trackers, no ads, no telemetry. None. There is no third-party SDK phoning home — no Firebase, no Sentry, no crash reporters, no "anonymous usage stats."
- The Android app makes zero network connections in its default configuration. You can watch it stay silent.
- One optional, opt-in exception: real measured flight-path reference images from the public DiscIt API. It's off by default; when off, no request is ever made. When on, it fetches a single image per disc on demand and caches it. That's the only outside service either surface will ever touch — and only if you ask it to.
- Your data moves the way you move it. Export to CSV, or use the app's full backup file, and carry it to a new phone yourself. Nothing leaves a device unless you send it.
- Even the "learning" is local. Disc Suggest's swipe-away preferences (Buy mode's sense of which flight numbers and brands you're passing on) are derived and stored entirely on-device, never transmitted anywhere, and reset anytime from the Disc Suggest screen.
- Open source (GPLv3). The code is here to read. The Android app is built to be F-Droid-reproducible — no proprietary blobs, a pinned toolchain, and a clean dependency tree — so the binary can be verified against this source.
┌─────────────────────────────┐ ┌──────────────────────────────┐
│ WEB APP (VPS) │ │ ANDROID APP (on phone) │
│ Flask · SQLite · vanilla JS │ │ Expo / React Native · SQLite │
│ secondary, simpler surface │ │ primary · canonical build │
└──────────────┬──────────────┘ └───────────────┬──────────────┘
│ │
└──────────────┬─────────────────────────┘
│ shared foundation
┌────────────────┴────────────────┐
│ • 1,660+ disc library (bundled) │
│ • flight-arc physics model │
│ • disc-suggestion scoring │
└──────────────────────────────────┘
The Android app is the reference implementation now — every feature runs on-device against local SQLite, including a from-scratch TypeScript reimplementation of the flight physics, so it works in a field with no signal exactly as well as it does at home. New behavior is designed against the app first; the website isn't required to keep up feature-for-feature.
The web app is deliberately boring in the best way: Flask, a single SQLite file, and vanilla JavaScript with no build step. It supports multiple local profiles (a picker on launch — still no passwords). It stays maintained as a lighter secondary surface.
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| Flight Shaper — shape the arc with sliders | Disc Suggest — ranked picks for a shot |
- Bag management — search 1,660+ discs, auto-fill flight numbers, assign colors, drag to reorder, filter by stability/type.
- Flight-path arcs — top-down visualization shaped by speed/glide/turn/fade, colored by stability.
- Flight Shaper — adjust hyzer, nose, wind, arm power, and spin; watch the arc and distance estimate update live. Optional physics-sim mode (below).
- Disc Suggest — recommends discs for 12 shot shapes, from your bag and the full library.
- Today's bag — check off what's in the bag today; export a filtered CSV.
- Multi-user — profile picker on launch, each profile its own bag.
Five tabs, all working offline. Confirmed on real hardware; preview APKs live on the Releases page for sideloading, now signed with the production release key. Also installable via a self-hosted F-Droid repo — add that URL in an F-Droid client for update checks without the Play Store. The official F-Droid index and Play Store are still ahead.
The whole UI went through a design-audit pass in v0.26: one shared set of controls and drawn
icons instead of five look-alike variants, every tap target at Android's 44dp minimum, the
hardware Back button behaving mid-round, and no screen relying on colour alone to tell you
something.
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| Bag | Flight Shaper | Disc Suggest | Score | Settings |
- Bag — full CRUD from the disc library, per-disc flight-arc thumbnails, filters, colors, a Today's-Bag / Collection split that scales to big collections, and a shareable bag report (a clean image of your bag, straight to the Android share sheet).
- Flight Shaper — the slider tool with a live arc, plus an opt-in on-device physics sim.
- Disc Suggest — skill-aware recommendations (Beginner / Intermediate / Advanced) with great/good/marginal fit chips, and a swipe-to-demote gesture with undo.
- Score — a dead-simple offline scorekeeper for when the scoring app won't load or there's no signal: hole-by-hole, 1–8 players, running totals vs. par, saved rounds. No account, no course lookup, no GPS.
- Settings — throw view, skill level, opt-in reference images, a disc catalog picker (switch between the built-in library, the larger Try Discs catalog, or your own imported catalog file/URL), and full backup & restore (one file: discs + today's bag + settings + scorecards — saved straight to a folder you pick, or sent to another app if you'd rather; move to a new phone, no server).
The Flight Shaper turns throw conditions into stability shifts, then draws the arc:
| Slider | Range | Effect |
|---|---|---|
| Hyzer | ±30° | Positive = hyzer angle, increases fade |
| Nose | ±15° | Nose up = higher AOA, more understable |
| Wind | ±20 mph | Headwind = more understable (flips more); tailwind = more overstable |
| Crosswind | ±20 mph | Physics-sim mode only — lateral wind |
| Arm | 50–100% | Under-power shifts fast discs understable |
| Spin | 50–100% | Lower spin = reduced gyroscopic stability, more turn |
Stability is the net of turn + fade:
| Label | Net (fade + turn) | Color |
|---|---|---|
| OS (overstable) | ≥ 1 | Purple |
| ST (stable) | −1 to 1 exclusive | Green |
| US (understable) | ≤ −1 | Gold |
Physics based on Kamaruddin, Potts & Crowther (2018) — Aerodynamic Performance of Flying Discs. There's also an opt-in Physics sim mode — a real rigid-body flight simulator (shotshaper, GPLv3) — for driver-class discs. Research/experimental, off by default; on the phone it runs entirely on-device.
Want the web app on your own machine? It's a plain Flask app — no build step, no database to provision.
git clone https://github.com/flyboy-byte/disc-tracker.git
cd disc-tracker
python3 -m venv venv && source venv/bin/activate
pip install -r requirements.txt
python app.py # → http://localhost:5757The database and secret key are created for you in data/ on first run. (numpy/scipy/pyyaml
are only needed for the optional Physics-sim mode; everything else is Flask alone.) A systemd unit
(disc_tracker.service) and a deploy.sh are included for running it as a service.
For the Android app, grab an APK from the Releases page — no build required.
GPLv3 — see LICENSE.