What mode is best for blues?

TL;DR: for a standard major-key blues, Mixolydian matches the chords. For a minor blues, Dorian is the classic choice. And over both, the minor pentatonic/blues scale remains legal at all times — blues mixes major and minor on purpose.

Why blues breaks the normal rules

A 12-bar blues in A uses A7, D7, and E7 — three dominant 7th chords. In textbook harmony, dominant chords are tension that must resolve; in blues, they’re just… home. That’s why plain major scale sounds wrong over blues (its natural 7th fights the chords) and why blues players happily bend minor 3rds over major chords. The genre’s whole flavour is that friction.

Major-key blues: Mixolydian

A Mixolydian — A, B, C#, D, E, F#, G — is the major scale with the 7th flattened, which makes it agree with an A7 chord note-for-note. It gives you the sweet major 3rd and 6th that pentatonic alone doesn’t offer.

The pro move: follow the chords. A Mixolydian over A7, D Mixolydian over D7, E Mixolydian over E7. Each switch is only a note or two of change, and suddenly you’re "playing the changes" instead of coasting on one box.

Minor blues: Dorian

Over a minor blues (Am7 to Dm7 and back), A Dorian is the standard answer — its natural 6th (F#) is literally the 3rd of the D chord, so the scale agrees with both chords at once. Aeolian works too, but darker; Dorian is why a minor blues can groove instead of mope.

And the blues scale?

Always available. The minor pentatonic plus its flat 5th isn’t a "mode" — it’s an attitude layer that blues lets you smear over any of the above. The mature sound is the blend: pentatonic grit for the shout lines, Mixolydian sweetness for the answers.

Cheat sheet

Situation	Play	Why
Major blues, one scale for everything	minor pentatonic / blues scale	the classic rub; always works
Major blues, following the chords	Mixolydian per chord	matches every dominant 7th exactly
Minor blues	Dorian	natural 6th agrees with the iv chord
Slow minor blues, maximum drama	Aeolian	the flat 6th sobs on cue