What is action and how do I know if mine is too high?

Action is simply the distance between your strings and the top of the frets, and it's one of the most fundamental — and most misunderstood — settings on any guitar, because "high" and "low" are relative to what you actually want out of the instrument.

What action actually affects

Higher action requires more finger pressure to fret cleanly, which can mean more effort and fatigue, but it also generally reduces buzz and can allow for slightly more volume and sustain on an acoustic, since the string has more room to vibrate without hitting frets. Lower action is easier and faster to play but is more prone to buzzing if other parts of the setup (relief, fret levelness) aren't dialed in well to compensate.

How to tell if yours is genuinely too high

• You're pressing noticeably harder than feels reasonable to fret cleanly, especially in the first few frets.
• Barre chords are a struggle in a way that feels like more effort than technique should require.
• Bending strings, especially on electric, feels stiffer and more physically demanding than it should.
• Measuring at the 12th fret, you're seeing noticeably more clearance than typical specs for your guitar type.

What "too high" doesn't mean

It doesn't automatically mean something is broken. Plenty of guitars are set up with intentionally higher action for slide playing, certain fingerstyle techniques, or simply personal preference for a heavier feel. High action only becomes a problem when it's fighting against how you actually want to play, or when it's a symptom of something else going on rather than a deliberate choice.

The fix, generally

If it's just a setup preference issue, adjusting the saddle and/or nut height (and rechecking relief) usually solves it. If action has crept up gradually and nothing was deliberately changed, that's worth investigating further — it might be pointing at a structural cause rather than a simple adjustment.