How to Figure Out Chords From a Song by Ear
Figuring out chords by ear sounds like a separate talent, but it's really applying things already covered - finding the key (see [[how-to-find-key-of-a-song:the article on finding the key]]) and intervals (see [[guitar-intervals-explained:the article on intervals]]) - to a specific recording, step by step, not guessing from zero.
Start with the bass, not the guitar
The lowest note in a recording is almost always the current chord's root, and it's the easiest thing to isolate from the rest of the instruments, because the bass usually plays one note at a time, not a full chord. Find the bass note on your own guitar before trying to guess the whole chord.
Find the key first
Knowing the song's key (see the article on finding the key) narrows the likely chords down to 6-7 up front instead of all twelve possible ones - the vast majority of songs stick to chords within one key, rarely reaching outside it.
Major or minor - hear the third
Once the root is confirmed, work out whether the chord is major or minor - physically the difference is just one semitone in the third (see the article on intervals), but by ear major sounds brighter and more 'settled', minor darker and 'sadder'. This is where figuring-out most often goes wrong: the root is right, but the chord's color isn't.
Common progressions are ready-made templates to check against
The C-Am-F-G progression (and its equivalents in other keys) is one of the most common sequences in popular music, period (see the article on 10 chords). If the first two or three chords check out, it's worth checking whether the progression simply continues one of the known templates before guessing each next chord from scratch.
Check your guess by playing along with the recording
Play the guessed chord at the same time as the recording, not after it - if it's right, the sound blends into one; if not, there's an obvious dissonance or a sense that a note is about to 'slide'. That's the fastest way to confirm or rule out a guess, much faster than comparing from memory.
Try it in practice
Open chord trainer