DarkTimer

A darkroom timer for developing film at home.

Build or look up a recipe, then run a guided multi-phase timer with agitation cues. Installable, offline, and private: everything stays on your device.

Open DarkTimer →

Features

Timer	Multi-phase countdowns with agitation and phase-end cues by sound, screen flash, vibration, and notification. Keeps the screen awake, runs fullscreen, and resumes an interrupted session.
Safelight theme	Switches the whole interface to deep red on black, from the header or the timer controls.
Recipes	Build one by hand, search the built-in development chart, or ask Gemini or Mistral with your own API key.
Library	Save presets, and review every past session with the exact recipe that was run.
Roll notes	Rate the negatives from each session (thin, good, dense), add notes, and re-run or save the recipe.
Chemistry	Track developer and fixer batches by mix date, expiry, capacity, and roll count, with optional reuse compensation.
Backup	Export presets, history, chemistry, and settings to a JSON file and restore them on another device.

The timer

DarkTimer runs any sequence of phases, such as Developer, Stop Bath, Fixer, Blix, and Wash.

• Agitation every 60 seconds, every 30 seconds, or stand, changeable mid-phase
• Cues you can tell apart in the dark: a 440 Hz beep and a short double pulse for agitation, an 880 Hz beep and one long pulse for phase end
• Pre-start countdown of 0, 5, or 10 seconds before each phase
• Yolo Run to move through every phase automatically
• Controls for start and pause, reset phase, skip phase (or swipe left), and mute
• Developer compensation from a custom percentage or a matching chemistry record

Beeps are scheduled ahead on the audio clock, so they stay on time even when the browser slows its timers down. Wake lock, vibration, fullscreen, and notifications depend on the browser; DarkTimer carries on without whichever is missing.

Recipes

Manual builder. Create black and white or colour (negative and slide) recipes with film, developer, dilution, ISO, temperature, phase durations, and agitation. Start one straight away or save it as a preset.

Lookup. The assistant checks the built-in development chart and your local cache first, and only then makes a live AI request. Gemini and Mistral are optional and use an API key you supply in Settings.

Warning

Chart and AI times are starting points, not authoritative processing instructions. Check anything that matters against the current datasheets from the film and chemistry manufacturers.

Privacy and offline use

DarkTimer has no account and no backend. Recipes, settings, chemistry, history, and cached lookups live in IndexedDB on your device.

• API keys go straight from your browser to the provider you chose. Keep them for the current session only, or save them in a local vault encrypted with a passphrase.
• Backups never contain API keys.
• Offline, everything works except a new live AI lookup. The built-in chart and previously cached results remain available.

Note

On iOS, Safari and the Home Screen app use separate storage. To move your data from one to the other, export a backup in Settings → History & Data and restore it on the other side.

Install

DarkTimer runs in any modern browser, and installing it gives the most app-like timer.

Platform	How
iPhone, iPad	Open the site in Safari, tap Share → Add to Home Screen, then launch it from the Home Screen.
Android, desktop Chrome or Edge	Use the browser's install button, or Install DarkTimer in its menu.

Development

Requires a current Node.js LTS release (22.12+ or 24). No API key is needed for manual recipes or the built-in chart.

npm install
npm run dev

The dev server runs at localhost:3000 and is reachable from other devices on your network, which is handy for testing on a phone.

Command	What it does
npm run dev	Start the dev server
npm run lint	Type check with TypeScript
npm run test	Run the Vitest suite once
npm run test:watch	Run tests in watch mode
npm run build	Build the production PWA into dist/
npm run preview	Serve the production build locally

Project layout

src/
  components/   UI: timer, recipe builder, library, chemistry, settings, assistant
  hooks/        React hooks for stored data and the API key session
  services/     Storage (IndexedDB), backup, recipes, dev chart, AI providers, PWA
  lib/          Small utilities

Stack

React 19 · Vite 8 · TypeScript · Tailwind CSS v4 · Motion · IndexedDB (idb) · Vitest · vite-plugin-pwa

DarkTimer is a web-only PWA deployed on Vercel. There is no native wrapper and no server component.

License

MIT. See LICENSE.