#React

How to Fix 'Hydration failed / Text content does not match' in Next.js

The complete guide to Next.js/React SSR hydration errors: why server and client renders diverge, the three usual suspects (timestamps, random values, localStorage), correct suppressHydrationWarning usage, and a ClientOnly pattern for browser-only widgets.

How to Fix 'Cannot read properties of undefined (reading map)'

A complete debugging guide for the most common React runtime error: why undefined.map throws, handling async data correctly, optional chaining and default guards, empty-state rendering, and using our JSON tools to inspect the real payload.