Acid Splash 5e FAQ FAQ
Can Acid Splash be used with Twinned Spell in D&D 5e?
No. Under the 2014 Twinned Spell rules and their official errata, Acid Splash is not eligible because the spell is capable of targeting more than one creature at its current level. This remains true even if the Sorcerer chooses only one creature for a particular casting. Twinned Spell checks what the spell is capable of targeting, not merely how many targets the caster happened to choose that time.
Acid Splash and Twinned Spell look compatible at first glance because Acid Splash can be cast at only one creature if the caster wants. The problem is that the 2014 Twinned Spell eligibility rule is stricter than simply counting the targets chosen for a particular casting. Official errata clarified that an eligible spell must be incapable of targeting more than one creature at the spell’s current level. Acid Splash can naturally select two creatures without any Metamagic, so it fails that requirement.
Acid Splash can already target two creatures
The 2014 Acid 
D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ Splash spell allows one or two visible creatures to be selected. The two targets must be within 5 feet of one another, but they are still two separate creatures affected by one casting.
That built-in second target is enough to make the spell capable of affecting more than one creature. The fact that the second target has a positioning restriction does not make Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ Splash a single-target-only spell.
Twinned Spell is therefore unnecessary as a way to make Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ Splash reach a second creature, and the eligibility rule prevents the Metamagic from being layered onto the spell for an additional target.
Twinned Spell checks what the spell is capable of targeting
The 2014 errata for Twinned Spell states that the spell must be incapable of targeting more than one creature at its current level. That wording focuses on the spell’s possible targets, not only the targets selected in the current casting.
Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ Splash fails that test because two creatures are an ordinary legal choice. Nothing has to be upcast, modified, or triggered for the spell to gain that capability.
This is why the answer differs from a genuinely single-target cantrip such as Ray of Frost. Ray of Frost cannot normally select a second creature, while Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ Splash can.
Choosing only one target does not make Acid Splash eligible
A Sorcerer 
D&D Portal - Sorcerer Character class A Charisma-based known-spell full caster whose Sorcery Points and Metamagic reshape spells in ways other casters cannot. Full link: https://dnd-portal.com/classes/sorcerer/ can cast Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ Splash at one creature when there is no suitable second target or when the caster simply prefers not to affect another creature.
That choice does not rewrite the spell into a single-target-only spell. It remains capable of choosing two creatures under the same spell description and at the same spell level.
Twinned Spell therefore cannot be enabled by voluntarily using fewer targets. Eligibility is determined by the spell’s rules, not by intentionally declining one of its available targets.
Being a cantrip is not what prevents Twinned Spell
Twinned Spell can work with eligible cantrips. The 2014 feature even specifies a sorcery-point cost for twinning a cantrip.
Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ Splash is disqualified because of its targeting capability, not because it is level 0, deals Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/, or uses a saving throw 
D&D Portal - Saving Throw D20 test rule Saving Throw is a d20 test rule used to resolve
uncertain outcomes during play. Full link: https://dnd-portal.com/rules/d20-tests/saving-throw/.
A different cantrip that targets only one creature and satisfies the other Twinned Spell requirements can still be a valid choice.
Other Metamagic options are separate questions
Failing the Twinned Spell requirements does not mean Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ Splash is incompatible with every Metamagic option. Each Metamagic feature has its own trigger and restrictions.
For example, a Metamagic option that modifies a saving throw D&D Portal - Saving Throw D20 test rule Saving Throw is a d20 test rule used to resolve
uncertain outcomes during play. Full link: https://dnd-portal.com/rules/d20-tests/saving-throw/, casting time, range, or components has to be evaluated under that option’s own wording rather than under the Twinned Spell restriction.
The important point is that Twinned Spell has a specific multi-target limitation. Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ Splash violates that limitation before any decision is made about which one or two creatures are actually chosen.