---
title: lookupNamespaceURI
framework: WebKit JS
role: symbol
role_heading: Instance Method
platforms: [Safari Desktop 3.0+, Safari Mobile 2.0+]
path: webkitjs/node/1634240-lookupnamespaceuri
---

# lookupNamespaceURI

## Declaration

```data
DOMString? lookupNamespaceURI(
    DOMString? prefix
);
```