# SyntaxError: Identifier 'x' has already been declared

**Code:** `already declared` · **Category:** JavaScript · **Seen on:** JavaScript

The same let/const/class name was declared twice in the same scope.

## Meaning

Often caused by including the same script twice, redeclaring in the browser console, or two scripts sharing global scope.

## Common causes

- Script loaded twice
- Duplicate declaration in one scope
- Re-running code in the console

## Quick fix

1. Rename or remove the duplicate
2. Load each script once
3. Wrap scripts in modules or IIFEs

## Detailed fix by platform

### JavaScript

1. Use `type="module"` scripts so each file has its own scope

## How to diagnose

1. **Name** — Which identifier?
2. **Load** — Is the script included twice?

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Source: [WhatIsMyError](https://whatismyerror.com/errors/javascript/syntaxerror-identifier-has-already-been-declared)