# querySelector APIs Running With Lightning Locker

When Lightning Locker is enabled, components that use `element.querySelector` or `element.querySelectorAll` APIs to return elements can encounter memory leaks and performance problems with large DOM trees.

:::note
For Lightning web components, `element` refers to the `this.template` prefix. For Aura components, `element` refers to the `this` prefix.
:::

When the component is removed from the DOM, the memory sometimes isn’t released. Garbage collection doesn’t clear the memory even if you manually invoke garbage collection in DevTools. The browser can use increasing amounts of memory, and potentially crash with an out-of-memory error.

The only workaround for this issue is to [enable Lightning Web Security](/docs/platform/lightning-components-security/guide/lws-enable.md) in the org where the component runs. Garbage collection works correctly under LWS.

Alternatively, if you're developing Lightning web components, consider using [refs](/docs/platform/lwc/guide/create-components-dom-work.md#refs) instead of `querySelector`.

**See Also**

- [*Lightning Web Components Developer Guide*: Access Elements the Component Owns](/docs/platform/lwc/guide/create-components-dom-work.md)