Can AI build a time tracker app like Toggl Track?

Build me a personal time tracker web app. Requirements:

- A single-page app: plain HTML, CSS, and vanilla JavaScript. No framework, no build step, no account, no server. All data stored in the browser via localStorage.
- A project list I define myself, each with a name and a color.
- A start/stop timer with a text description field, tied to one project.
- Only one timer can run at a time — starting a new one auto-stops whatever is currently running.
- Manual entry: let me add or edit a time block by typing a start time, end time, and project, for time I forgot to track live.
- Handle these cases correctly, not just the simple "timer running normally" one:
  1. Browser refresh or tab close while a timer is running: on reopening, the timer should still show as running with the correct elapsed time, calculated from a stored start timestamp — not from a countdown that resets.
  2. A manual entry that crosses midnight: split its duration correctly across the two calendar days it touches when computing daily totals.
  3. Editing a past entry's project or times: recalculate that day's and that week's totals, don't just leave stale totals in place.
- A daily view and a weekly view, each showing total time per project as a simple bar list.
- A one-click "export all data to CSV" button — this is the backup, since there is no account or server.
- Nothing that requires publishing, an App Store, or any account of any kind. This only needs to run in my own browser.
- Include a short README explaining that data lives only in this browser and how to export/restore it.
  Keep the whole thing well under 500 lines — this is a personal tool, not a product.

What is the short answer?

If you’re tracking your own billable hours from one computer, AI can build you a timer that does 90% of what you actually use Toggl Track for: start/stop tracking, projects, tags, daily totals, and a CSV you can hand to a client or drop into a spreadsheet for invoicing. You’re paying $9–10/mo mostly for sync across devices and polished reporting — cut those two things and the app is genuinely simple.

It’s worth building if you track time on one machine and just need the number at the end of the week. It’s not worth building if you switch between a laptop and phone throughout the day and need the same running timer on both — that needs a backend, which turns this from an afternoon project into a small service.

What should the first version include?

• Start/stop timer with a text description
• Project field (a short list you maintain yourself, color-coded)
• Manual add/edit for entries you forgot to start live
• Daily and weekly totals, grouped by project
• CSV export button
• Deliberate exclusion: no team members, no client billing rates, no invoice generation — that’s a different app (see the Invoice Ninja build)

What can AI build reliably?

A timer that starts, stops, and persists to local storage is straightforward for ChatGPT, Claude, or Lovable to produce correctly on the first or second try. Grouping entries by day/project and summing durations is basic arithmetic AI handles without issue. A simple bar chart of hours per project (via Chart.js or a hand-rolled SVG) is also reliable. CSV export is a few lines of JavaScript and rarely needs a second pass.

Where will AI need human help?

Idle detection is the first wall — Toggl’s desktop app watches for keyboard/mouse inactivity and prompts you to discard idle time; a web page in a browser tab can’t see system-wide activity, so you’ll need to trust yourself to stop the timer. Sync across devices is the second wall: without a backend, your data lives in that one browser’s local storage, so switching computers means starting a separate, disconnected log. If you genuinely need two devices, the honest fix is a lightweight backend (Supabase or Firebase) that AI can also help wire up, but that moves this from “no ongoing cost” to a small monthly database bill and a bit more setup.

For personal use, decide up front whether you’re a one-device or multi-device tracker — that answer determines whether this stays a weekend build or becomes a slightly bigger one.

How long will it take and what will it cost?

A rough prototype — timer, projects, local storage — is an afternoon, roughly 2–4 hours with ChatGPT or Claude walking you through it. A version you’d actually rely on daily (manual edit/delete, weekly summary view, CSV export, and enough polish that you trust the numbers) is closer to a full day spread over a few sessions.

Against Toggl Track Starter at $9–10/mo, even a full day of build time pays for itself within the first month or two if you were going to keep paying indefinitely. There’s no ongoing cost with local storage — the trade is your time now for no subscription later.

Which AI tool or approach should I use?

• ChatGPT or Claude in a browser conversation: best for a plain HTML/CSS/JS build with no setup — paste the starter prompt below and iterate in place.
• Lovable or a similar conversational builder: better if you want a nicer default UI (cards, charts) without hand-tuning CSS yourself, at the cost of a small learning curve on their interface.
• Cursor: only worth it if you’re already comfortable in a code editor and want to version-control the project or add the multi-device backend later.

For a single-user, single-device timer, ChatGPT/Claude producing a self-contained HTML file is the fastest path — there’s no backend to configure.

What will I need to maintain?

Nothing, if it stays local-storage-only: no hosting, no accounts, no API costs. The trade-off is that clearing your browser data or switching browsers wipes your history unless you export first — get in the habit of exporting CSV weekly as your backup. If you later add a backend for sync, you take on a small recurring cost (Supabase/Firebase free tiers cover this scale, so likely still $0–$5/mo) and the responsibility of keeping your own API keys private.

Should I build it, buy it, or reduce scope?

Build it if you track time from one device and mainly need the weekly total for invoicing or your own awareness.

Buy it (keep Toggl) if you already rely on cross-device sync, idle detection, or Toggl’s integrations (Slack, calendar, Asana) — replicating those isn’t a weekend project.

Reduce scope if even a timer feels like overhead — a plain spreadsheet with start/end times you type in by hand costs nothing and takes zero build time; only build the app once manual logging in a sheet has actually annoyed you.

What if I wanted to ship this to other people?

Multi-user support means every timer needs to belong to an account, which means real authentication, a database instead of local storage, and a plan for what happens when two people’s data collides. You’d also want server-side timer state so a dropped connection doesn’t lose someone’s running entry. That’s a different, ongoing project — not a variation on the weekend build above.

Starter build specification

• User: you, for your own use
• Problem: replacing Toggl Track’s paid tier for solo time tracking
• Core workflow: pick a project → start timer → stop timer → see daily/weekly totals → export CSV
• Required features: start/stop timer, project tagging, manual entry/edit, daily/weekly totals, CSV export
• Deliberate exclusions: no accounts, no multi-device sync, no team features, no client billing rates, no App Store submission
• Data ownership: stored in the browser’s local storage; CSV export is the backup/portability mechanism
• Definition of done: you can start a timer, stop it, see it show up correctly in today’s and this week’s totals, and export a CSV that opens cleanly in a spreadsheet

Sources and verification

Pricing checked September 17, 2026 against Toggl Track’s official pricing page and third-party pricing trackers, showing Starter at $9–10/user/month depending on billing cycle. Export/API behavior checked against Toggl’s own data export documentation. This article is a reviewed build plan, not a tested build — no working prototype was built or run for this piece.

Reviewed on September 17, 2026.