You Readied an Attack. Your Second Swing Didn't Come With It.

Readying an action is one of the most misplayed rules in D&D, and the Extra Attack trap is the part that catches even experienced tables.

Say the party sets up an ambush at a chokepoint: a narrow stairwell, one door in, one door out. The fighter takes position at the top of the stairs and readies an attack for "the first creature that walks through that door." A bandit kicks it open a minute later, the trigger fires, and the fighter swings. Once. Even with Extra Attack on the character sheet, which would normally mean two.

That's not a DM being stingy. It's the rule working exactly as written, and it trips up tables constantly because Extra Attack and the Ready action look like they should stack, and don't.

What Ready actually buys you

Readying happens on your turn: you pick a perceivable trigger (the door opens, the caster starts a spell, the signal flare goes up) and you pick exactly one thing to do in response, either a single action or movement up to your speed. Not your whole turn, not an action plus a bonus action. One of the two, chosen in advance, tied to a condition that actually has to happen, not something you're guessing might.

When the trigger fires, that stored response becomes your reaction. You can take it right after the trigger resolves, or let it go if you change your mind. Nothing forces you to act just because the thing you were waiting for happened.

Where Extra Attack falls apart

Extra Attack is written to trigger when you take the Attack action on your own turn. A readied attack isn't the Attack action on your turn, it's a single attack delivered through your reaction on someone else's. Jeremy Crawford confirmed the ruling directly: the second swing doesn't come along for the ride. A level 11 fighter who readies "attack the first thing through the door" gets exactly the one hit a level 1 fighter would get in the same spot. Ready is more valuable before a character picks up Extra Attack, not after, which is the opposite of what most players assume going in.

The reaction you forget you're holding

Readying spends your reaction for the round the moment you commit to it, not the moment the trigger fires. If something else demands a reaction first, an opportunity attack, a Shield spell, whatever, the readied action is already gone even if the trigger you were waiting for never shows up. And if the trigger simply doesn't happen before your next turn starts, the readied action evaporates on its own. No refund, no carryover.

If what you readied was a spell, the resources were already spent when you cast it to hold it, so an unused readied spell is a slot you don't get back, not just a missed opportunity. Holding a readied spell also costs Concentration for as long as you're holding it, which means anything that would normally break Concentration, getting hit, mostly, can pop it before the trigger even arrives.

Tracking it so it doesn't get lost

The actual failure mode at most tables isn't misreading the rule, it's forgetting the readied action exists at all three rounds later when the trigger finally shows up in the middle of an unrelated exchange. If you're running the fight in Virtual Combat Simulator, the condition field on a token is the obvious place to park it: a note like "Readied: attacks first through the door" sitting next to that character's hit points means the trigger firing mid-combat doesn't depend on anyone's memory. The token says what's being waited for, and whoever's running the scene can resolve it the moment it's actually earned.

Decide the trigger and the one thing you're doing about it at the same time, write it down somewhere you'll actually see it, and don't count on a second swing showing up that the rule never promised you.

You Readied an Attack. Your Second Swing Didn't Come With It.