# Error: Minified React error #31; visit https://react.dev/errors/31 for the full message

**Code:** `Minified React error` · **Category:** React · **Seen on:** React

A production React build threw an error whose message was shortened to a number.

## Meaning

Production builds strip messages. The URL decodes the full message; reproduce in development to get the full error and component stack.

## Common causes

- Same root causes as development errors (invalid child, hooks, hydration)
- Production-only differences (env vars, data)

## Quick fix

1. Open the URL in the message to read the full text
2. Reproduce with a development build
3. Use source maps in your error monitoring

## Detailed fix by platform

### React

1. Common numbers: #31 objects as child, #130 invalid element type, #418/#423/#425 hydration mismatches

## How to diagnose

1. **Number** — Which error code?
2. **Reproduce** — Same in development?

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Source: [WhatIsMyError](https://whatismyerror.com/errors/react/minified-react-error)