> For the complete documentation index, see [llms.txt](https://shopify-1.gitbook.io/react/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://shopify-1.gitbook.io/react/3.-advanced-topics/performance-optimizations/purecomponent.md).

# PureComponent

`React.PureComponent` is exactly like `React.Component` but implements `shouldComponentUpdate()` with a shallow prop and state comparison.

If your React component’s `render()` function renders the same result given the same props and state, you can use `React.PureComponent` for a performance boost in some cases.

**When to use PureComponent vs Stateless (functional) components** One question that often comes up is whether to use Stateless (functional) components or PureComponent.

For simple, presentational-only components that need to be easily reused and don’t require state, prefer [stateless functional components](https://shopify.gitbooks.io/react/content/1_Introduction/2.%20Components/2.1%20-%20Stateless%20Components/). The ESLint rule `[react/prefer-stateless-function](https://github.com/Shopify/eslint-plugin-shopify/blob/master/lib/config/rules/react.js#L63)` currently enforces this pattern when using the [eslint-preset-shopify](https://github.com/Shopify/eslint-plugin-shopify/) preset.

This way you're sure they are decoupled from the actual app logic, that they are dead-easy to test and that they don't have unexpected side effects. The exception is if for some reason you have *a lot* of them or if you really need to optimise their render method (as you can't define `shouldComponentUpdate` for a stateless functional component).

One might be tempted to think that functional components would be more performant and have less overhead than class-based components, but this is currently not the case. Internally, stateless component are wrapped in a class and follow the same code path as classed-based components. However, the React team has mentioned that they intend to work on improving the performance of stateless functional components in the future. The original [React 0.14 release notes](https://facebook.github.io/react/blog/2015/10/07/react-v0.14.html#stateless-functional-components) confirms this:

> **In the future**, we’ll also be able to make performance optimizations specific to these components by **avoiding unnecessary checks and memory allocations**.