Invisible: who can see you matters

SRD 5.2.1 · Conditions

At the table

1. If Initiative is rolled while Invisible, apply Advantage to that roll.
2. An effect requiring a seen target cannot affect you unless its creator can somehow see you. Carried and worn equipment is concealed too.
3. Apply the attack benefits, except against a creature that can somehow see you. The condition is not a blanket rule for being unheard.

Example decision

An Invisible scout attacks a sentry that can somehow see the scout. Does Invisible itself give that attack Advantage against this sentry?

No; the condition’s attack benefit does not apply against that observer.

The attack benefit explicitly stops applying against a creature that can somehow see you. Resolve other sources of Advantage normally. The same observer-dependent idea matters for effects that require a target to be seen. Read the observer’s ability to establish what it actually perceives and under which conditions.

Watch for this mistake

Do not equate Invisible with silent, untrackable or automatically hidden. Hiding has its own requirements and ending triggers. A particular invisibility effect may also have its own duration and termination rules.

Ask the table

Which creature is observing, what allows it to see you, and does the chosen effect require sight?

Source rule

While you have the Invisible condition, you experience the following effects. Surprise. If you’re Invisible when you roll Initiative, you have Advantage on the roll. Concealed. You aren’t affected by any effect that requires its target to be seen unless the effect’s creator can somehow see you. Any equipment you are wearing or carrying is also concealed. Attacks Affected. Attack rolls against you have Disadvantage, and your attack rolls have Advantage. If a creature can somehow see you, you don’t gain this benefit against that creature.

Source: SRD 5.2.1, 184. Online guide.