alexmerced.app

A shelf of small browser tools. Every one runs entirely on the visitor's own machine, stores its data locally, and exports the whole dataset to a file on request. There is no server, no account, and no analytics.

Live at https://alexmerced.app

The apps

Writing and notes

App	What it is
Warren	Nested pages built from blocks, with markdown shortcuts, a slash menu, search, trash, and Markdown export
Jotterbug	Quick notes on a coloured board: pinning, labels, checklist mode, archive and trash, both reversible

Planning and time

App	What it is
Laneway	A kanban board for one person: WIP limits, checklists, due dates, labels, drag and drop, keyboard moves, archive
Stint	A time tracker with projects, rates, billing rounding, day and week views, and CSV export
Rote	Spaced repetition on SM-2, with a fortnight forecast, retention stats, and CSV import and export

Data tools

App	What it is
Decanter	Convert between JSON, NDJSON, CSV, YAML and TOML; flatten, query by path, and generate SQL, Iceberg or JSON Schema
Fabler	Seeded sample data with foreign keys that keep referential integrity, out as JSON, CSV, SQL or DDL

Making files

App	What it is
Tessera	A QR generator with nine payload builders, a from-scratch encoder, and a saved library
Loupe	Resize, convert and compress images, reading EXIF first so you can see what re-encoding strips
Quire	Merge, split, reorder and rotate PDF pages, and turn images into pages
Rostrum	Slide decks with a presenter view, Markdown in and out, and PDF or standalone HTML export

Working things out

App	What it is
Reckoner	An expression calculator with a tape, memory registers, and thirty functions
Sift	A regex workbench with live highlighting, capture groups, replacement preview, and a plain English explainer

Running it

npm install
npm run dev       # http://localhost:4321
npm test          # 836 tests
npm run build     # writes dist/ and generates the service worker
npm run preview   # serve the built site, needed to exercise the PWA

How it is built

Astro 5 with no UI framework. Each app is plain TypeScript split into three parts, which is what makes it testable:

• model.ts is pure logic with no browser APIs: the page tree, card movement, note filtering, the QR encoder. This is where the test suite lives.
• store.ts wraps persistence and the export and import envelope.
• ui.ts owns the DOM.

Shared plumbing sits in src/lib: a promise wrapper over IndexedDB, a localStorage helper that degrades to memory when storage is blocked, the export format, toasts, and the PWA registration.

Written from scratch, not pulled in

The site has no runtime dependencies at all. Where a library would normally be reached for, the thing is implemented here and covered by tests:

• A QR encoder implementing ISO/IEC 18004 (src/apps/tessera/qr.ts).
• A PDF writer using the standard fourteen fonts with real AFM metrics, so text can be measured rather than guessed (src/lib/pdf/write.ts).
• A PDF reader that parses cross-reference tables, cross-reference streams and object streams, enough to move pages between files (src/lib/pdf/parse.ts).
• Parsers for JSON, NDJSON, CSV, YAML and TOML (src/apps/decanter/formats.ts).
• SM-2 spaced repetition (src/apps/rote/model.ts).
• An EXIF reader (src/apps/loupe/exif.ts), a ZIP writer with CRC-32 (src/lib/zip.ts), and a seeded PRNG (src/lib/random.ts).

The QR encoder

src/apps/tessera/qr.ts implements ISO/IEC 18004 from scratch rather than pulling in a dependency: numeric, alphanumeric, and byte modes across all forty versions and four error correction levels, Reed-Solomon over GF(2^8), and all eight data masks scored by the four penalty rules.

Its tests do more than check that it runs. They verify all 160 version and level capacities against the published table, confirm every Reed-Solomon syndrome is zero (the defining property of a valid codeword), and read the finished matrix back through a decoder to check that what comes out is what went in, under every mask and across versions that exercise alignment patterns and version blocks.

Export and import

Every app writes the same envelope:

{
  "format": "alexmerced.app/export",
  "version": 1,
  "app": "warren",
  "appVersion": 1,
  "exportedAt": "2026-08-30T09:00:00.000Z",
  "counts": { "pages": 12 },
  "data": { "pages": [] }
}

Import validates the envelope before touching anything, refuses a file from a different app, and offers merge or replace. Merging resolves conflicts by keeping whichever copy was edited most recently. Records that arrive malformed are repaired or dropped rather than allowed to corrupt the store: an orphaned page is reparented, a parent cycle is broken, an unknown block type becomes a paragraph.

Progressive web app

The site installs to a phone or desktop and works with no network at all.

scripts/build-sw.mjs runs after astro build. It walks dist/, collects every page and asset, and writes dist/sw.js with that precache list and a version hashed from the content plus the worker's own source, so a deploy always invalidates the previous cache. The worker precaches on install and then serves cache-first while refreshing in the background.

One thing worth knowing if you adapt this: cache lookups pass { ignoreVary: true }. Servers commonly send Vary: Origin on JavaScript, and module scripts are fetched in cors mode while cache.addAll stores them from a no-cors request. Without ignoreVary the scripts never match the cache and the site loads offline with no JavaScript at all.

Known limits, stated plainly

• PDF text uses the standard fourteen fonts, which are Latin-1. CJK and emoji would need font embedding and subsetting.
• Quire refuses encrypted PDFs rather than mangling them, and does not render page thumbnails; preview goes through the browser's own PDF viewer.
• Decanter's YAML and TOML support is a documented subset. No anchors, aliases or tags in YAML.
• Everything is held in memory, so very large files will strain a phone.

Storage, and its limits

IndexedDB and localStorage are scoped to one browser on one device. Nothing syncs, because nothing leaves. Clearing site data deletes it, and private windows usually discard it on close. That is the trade the site makes in exchange for never seeing your data, and it is why every app has an export button.

License

MIT for the code. See LICENSE.