10 Signs of a Bad Macaron

"...

1. Air bubbles

2. Cookie shells that separate from the cookie itself

3. Excessive coloring

4. Substituting ground almonds for pistachios

5. The almond extract issue

6. Stale macarons

7. Macarons that are too big or too small

8. Almond flour not ground finely enough

9. Too much sugar

10. Too little filling"

 

(Source and more details: Link)

 

Macaron Tasting @ Berlin Mitte Food Tour
Macaron Tasting @ Berlin Mitte Food Tour