The plain-English version
Connecting client-side application behavior to markup that was initially rendered elsewhere, commonly on a server.
Why it matters
Hydration requires the client's initial output to match the server-rendered markup expected by its framework; React treats mismatches as bugs.
Let’s make it click
A server-rendered counter becomes interactive when the browser initializes its component state and handlers.
Vibe Bro’s heads-up
Reading browser-only data during initial rendering can make the first client result disagree with the server output.
The docs behind it
Documentation links checked .
Editorial review · October 28, 2026
Corrected: Replace 'agree well enough' with the explicit initial-output matching requirement documented by React, avoiding the suggestion that mismatches are generally acceptable.