# `Error: Hydration failed because the server rendered HTML didn't match the client.`

**Where it appears:** Browser console

**What it means:** The page looked one way when the server built it and another way in the browser.

## Likely causes

- Something different on each side, like the current time or a random number.
- Reading browser-only data (like saved settings) while the page first renders.

## Message for your agent

```text
The browser console says “Hydration failed”. Find which component renders differently on the server and the client, fix it, and explain the cause in one sentence.
```

**Prevention:** Read browser-only data after the page loads.

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Source: [Agentic Makers](https://agenticmakers.app/en/help/errors/hydration-failed) · License: CC BY 4.0