---
title: "prewarm | JavaScript maps SDK"
description: "Documentation for MapTiler SDK"
---

> For AI agents: a documentation index is available at [/llms.txt](https://docs.maptiler.com/llms.txt). Markdown versions of all pages are available by appending .md to any URL.

# Variable prewarm

prewarm: () \=> void

#### Type Declaration

-   -   (): void
    -   Initializes resources like WebWorkers that can be shared across maps to lower load times in some situations. `setWorkerUrl()` and `setWorkerCount()`, if being used, must be set before `prewarm()` is called to have an effect.
        
        By default, the lifecycle of these resources is managed automatically, and they are lazily initialized when a Map is first created. By invoking `prewarm()`, these resources will be created ahead of time, and will not be cleared when the last Map is removed from the page. This allows them to be re-used by new Map instances that are created later. They can be manually cleared by calling `clearPrewarmedResources()`. This is only necessary if your web page remains active but stops using maps altogether.
        
        This is primarily useful when using GL-JS maps in a single page app, wherein a user would navigate between various views that can cause Map instances to constantly be created and destroyed.
        
        #### Returns void
        
        #### Example[](#example)
        
        ```typescript
        prewarm()
        ```