This free online metronome keeps steady time for practice, from a slow 20 BPM to a blistering 300. Set the tempo with the slider, the plus and minus buttons, or tap it in. Choose a time signature from 2/4 to 12/8, then tap any beat to accent it, leave it normal or silence it, so you can practise with the click only on beats 2 and 4, or only on the downbeat. Add eighth notes, triplets, sixteenths or a swing feel, and pick a click, woodblock or beep sound.
The speed trainer raises the tempo by a set number of beats per minute every few bars, up to a target you choose, which is the quickest way to bring a hard passage up to speed. Clicks are timed by the browser audio clock rather than a timer, so the beat stays rock steady, and the screen stays awake while it runs. Space starts and stops it, and your settings are kept in the page address so you can bookmark a practice tempo.