[RPG] What determines the ability used for a saving throw


I'm new to D&D. I was reading about save throws in the Player's Handbook and saw this:

To make a saving throw, roll a d20 and add the
appropriate ability modifier. For example, you use your
Dexterity modifier for a Dexterity saving throw.

What determines what type of saving throw it is? The DM? The attack cast on the PC? Or do you add your highest ability modifier to the d20 rolled?

Best Answer

The effect specifies the saving throw required, but it's ultimately up to your DM.

When a saving throw is required, the effect that caused the saving throw specifies what kind of saving throw it is. For instance, the spell Acid Splash states that (emphasis mine):

You hurl a bubble of acid. Choose one creature within range, or choose two creatures within range that are within 5 feet of each other. A target must succeed on at Dexterity saving throw or take 1d6 acid damage.

So if your character was targeted by an acid splash, a Dexterity saving throw would be required.

Any effect described in the rulebooks which requires a saving throw always specifies the type of saving throw required... but the DM is the ultimate arbiter of the rules, and they are free to ask for a different kind of saving throw instead, or ask for saving throws due to circumstances of their own devising not explicitly described in the rules, if it makes sense to them, as described in the DMG's section about adjudicating saving throws (DMG p.238):

Most of the time, a saving throw comes into play when an effect - such as a spell, monster ability, or trap - calls for it, telling you what kind of saving throw is involved and providing a DC for it.

Other times, a situation arises that clearly calls for a saving throw, especially when a character is subjected to a harmful effect that can't be hedged out by armor or a shield. It's up to you to decide which ability score is involved. The Saving Throws table offers suggestions.