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## Resource: About Warmup Data

## Article: About Warmup Data

## Article Link: https://dev.wix.com/docs/develop-websites-sdk/code-your-site/build-a-custom-frontend/page-rendering/about-warmup-data.md

## Article Content:

# About Warmup Data

Warmup data is used to optimize [page rendering](https://dev.wix.com/docs/develop-websites-sdk/code-your-site/build-a-custom-frontend/page-rendering/about-page-rendering.md) when your site's pages are rendered on both the server and the client, ensuring that costly data operations are done only once.

Generally, the server executes data operations faster than the browser. With warmup data, you can pass the results of your server operations to your frontend code. During browser rendering, you can write code to check if those operations were already done and set to warmup data, and if the warmup data exists, use it in your code. This prevents the client from performing the same expensive operations again.

Use the [Rendering API](https://dev.wix.com/docs/sdk/frontend-modules/window/rendering/introduction.md) to check whether your code is being run on the client or the server, and the [Warmup Data API](https://dev.wix.com/docs/sdk/frontend-modules/window/warmup-data/introduction.md) to set and get the warmup data.

## Supported IDEs

You can optimize page rendering with `warmupData` using:

- The [editor](https://dev.wix.com/docs/develop-websites-sdk/code-your-site/developer-environments/ides/code-editor/about-the-code-editor.md) (Wix Studio and Wix Editor)
- The [Wix IDE](https://dev.wix.com/docs/develop-websites-sdk/code-your-site/developer-environments/ides/wix-ide/about-the-wix-ide.md) (Wix Studio)
- Your [local IDE](https://dev.wix.com/docs/develop-websites-sdk/code-your-site/developer-environments/ides/git-integration/about-git-integration-with-wix-cli.md) (Wix Studio and Wix Editor)

## Browser rendering

When working with warmup data it's important to keep in mind that there may be cases where browser rendering happens before server-side rendering. In such cases, you can't rely on the warmup data being set on the server, and need to execute those operations directly on the client-side.

Note that you can only perform the following operations in the browser:

- Access the browser's storage
- Use 3rd-party analytics
- Create dynamic event handlers
- Retrieve information about the client's browser
- Navigate to another page

## See also

- [About page rendering](https://dev.wix.com/docs/develop-websites-sdk/code-your-site/build-a-custom-frontend/page-rendering/about-page-rendering.md)
- [Optimize page rendering with warmup data](https://dev.wix.com/docs/develop-websites-sdk/code-your-site/build-a-custom-frontend/page-rendering/optimize-page-rendering-with-warmup-data.md)