---
title: Sloppy mode
slug: Glossary/Sloppy_mode
tags:
  - CodingScripting
  - Glossary
  - JavaScript
  - Sloppy
---
{{Glossary("ECMAScript")}} 5 and later let scripts opt in to a new [strict mode](/en-US/docs/Web/JavaScript/Reference/Strict_mode), which alters the semantics of JavaScript in several ways to improve its resiliency and which make it easier to understand what's going on when there are problems.

The normal, non-strict mode of JavaScript is sometimes referred to as **sloppy mode**. This isn't an official designation, but you are likely to come across it if you spend time doing serious JavaScript code.

## See also

- "[Strict Mode](http://speakingjs.com/es5/ch07.html#strict_mode)" in chapter 7 ("JavaScript Syntax") in the book Speaking _JavaScript_.
