Rolling 1 or 20

Dice rolled

d20

Sometimes fate blesses or curses a combatant, causing the novice to hit and the veteran to miss.

Sage Advice

Spell attacks can score critical hits, just like any other attack.

Source: [Sage Advice > Compendium](http://media.wizards.com/2015/downloads/dnd/SA_Compendium_1.01.pdf)

If the d20 roll for an attack is a 20, the attack hits regardless of any modifiers or the target's AC. This is called a critical hit.

If the d20 roll for an attack is a 1, the attack misses regardless of any modifiers or the target's AC.