Timing you can rely on
Many browser metronomes drift because they rely on page timers, which slow down when the computer is busy or the tab is in the background. This metronome writes every click onto the clock of the audio system a moment in advance, so each click starts at the exact sample it belongs to. The beat stays steady while you switch to sheet music in another tab, and the screen stays on while it plays.
The dots show the beats of the bar; the first, accented beat has its own colour. The tempo name (Andante, Allegro, Presto...) is shown as a rough guide.
Time signatures, accents and subdivisions
The top number of the time signature is the number of clicks per bar, the bottom one the note value of a click. In 3/4 you hear three quarter-note clicks per bar, in 6/8 six eighth-note clicks with accents on the first and fourth, so you can feel the two groups of three. Switch off Accent first beat for an even click.
Subdivision adds softer clicks between the beats: two for eighths, three for triplets, four for sixteenths. They help with fast passages and with keeping a steady groove at slow tempos.
Tempo trainer
Turn on the tempo trainer to raise the speed automatically, for example by 5 BPM every 4 bars until 160 BPM. Start a difficult passage slowly, play it cleanly, and let the trainer push you a little at a time. The current goal and the bars until the next step are shown under the button.
Tap tempo
Tap the pad below the metronome along with a song, or press T on the keyboard. After a few taps you see the BPM, averaged over your last eight taps; Use this tempo sets the metronome to it. A pause of more than two seconds starts a new count.