Track Your Time от Ricos Labs LLC

Track Your Time is free, open-source time tracking for freelancers and small teams who bill by the hour. This add-on puts its timer in your Firefox toolbar. One click starts it, and the icon shows how long it has run.

Free, with nothing held back
There's no paid plan, now or later, and no premium tier. Every feature is in every install, the hosted version included. The code is open source under the AGPL-3.0 and built in the open on GitHub.

Your data lives where you choose
A time tracker knows who your clients are, what you charge them and how you spend each working day. Keep that on trackyourtime.dev, or on a server you run yourself. It's the same app either way, and this add-on works with both: choose "Change server" below the sign-in form. Take everything out as JSON or CSV whenever you like.

A timer that keeps up with you
Most of today's work is work you did yesterday. Start it again from your recent entries, or pin the jobs you do every day. Type the first letters of a description, and the add-on suggests ones you've used before. It can fill in the project and tags from last time too.

Lose the connection on a train, and keep tracking. The add-on saves your changes and sends them when you're back online. Stop a timer here, and the web app shows it stopped at once.

Already logged in to Track Your Time in Firefox? The add-on offers that account, and you confirm it in the popup. There's no extra password and no API key to copy. Accounts with two-factor authentication use "Sign in with the web app".

The hours you forgot
Add the time for a call you didn't time, or fix an earlier day before you bill it. Or turn on activity capture. The add-on notes which website had your attention and suggests entries for the gaps in your day. It stores the site's name, not the page, and nothing leaves your computer until you accept a suggestion.

From hours to invoice
The web app turns your hours into reports by client, project, task or person. It makes invoices as a PDF, or as a ZUGFeRD or XRechnung e-invoice. Invite your team, and each person sees only their own time until you share more.