on Fiction University:

Just because a character says it, doesn’t mean it isn’t an infodump.

Dialogue is one of my favorite parts of writing. It’s fast-paced, grabs attention, and usually keeps the reader reading. When two characters are having a zippy conversation, readers feel like they’re hanging out with them and are part of the story.

But those conversations can also contain the dreaded infodump-as-dialogue.

Infodumping (throwing in a lot of “need-to-know” information at one time) doesn’t just happen to prose. Characters can have conversations they’d never have, talking about things they’d never talk about, just so authors can explain things to readers.

Which is bad, because…

Infodumps remind readers they’re reading, and can knock them right out of the story.

Dialogue belongs to the character, and when you sneak in and take over their words, it makes them feel like puppets on a stage, not real people. When characters start spouting information instead of having conversations, it slows the pace and flattens the scene.