Safari's Describe Extension builds a browser extension from a sentence, within limits Apple spells outSafari's Describe Extension builds a browser extension from a sentence, within limits Apple spells out

Safari in iOS 27, iPadOS 27 and macOS 27 can create a browser extension from a plain-language description, using a feature Apple calls Describe Extension.

It runs on Apple Intelligence, so it needs a device that supports it. Apple lists the iPhone 15 Pro, iPhone 15 Pro Max and every iPhone 16 model or later, iPads and Macs with M1 or later, the iPad mini with A17 Pro, and the MacBook Neo. Apple's Safari guide adds that Apple Intelligence on macOS 27 is not available in all languages or regions and that usage limits may apply.

How do you create an extension in Safari?

Apple's Safari User Guide for macOS 27 gives these steps:

• Go to the website the extension is for.
• Click the Page Menu button in the Smart Search field and choose Describe Extension.
• Type what the extension should do, or pick one of the suggested categories.
• Safari checks the App Store for an existing extension that matches. Pick one of those, or click Create to build your own.
• Click the result to change it or Try to test it. While trying it, Edit makes further changes and Save keeps it.

On iPhone the entry point is the same Page Menu in the address bar, iDownloadBlog reports. Its writer used it to turn the site's white background grey and to make every image on a page black and white. Apple's own examples include a three-minute focus timer for a page and a button that closes duplicate tabs. A custom extension is removed with the Delete button in Safari's Extensions settings rather than Uninstall.

What Apple says these extensions cannot do

Apple's support page on Safari extensions sets three limits. A described extension cannot load remote content, cannot use third-party services and cannot access files on the Mac. Safari also checks that a request can be built as described, and asks for a rewrite if it cannot.

Those limits define the feature. A described extension can rearrange, restyle, hide or add to the page in front of it and act on tabs, but it cannot fetch anything from elsewhere, send what it sees to a server or touch the disk.

Our take

The three limits are the most important sentence Apple has written about this feature. An extension can read every page it runs on, which is why extensions have long been a route for stealing data. One that cannot load remote content or call outside services has nowhere to send what it reads. APPDOOK's reading is that Apple has confined generated code to the page so that a badly written request produces a broken extension rather than a leaky one.

Several things are still unclear. Apple does not say whether described extensions sync between devices the way App Store extensions can with Share across devices, whether they can be shared with anyone else, or whether each generation counts against the Apple Intelligence budget. Like Safari's Notify Me, which works inside limits Apple has not published, it falls under the same unpublished daily Apple Intelligence limits, so heavy tinkering may hit a ceiling nobody can see coming.

For extension makers the App Store step matters more than the generator. Safari searches the store before it offers to build anything, so a well-described extension with a clear name now gets a chance at every user who types a request. The extensions most exposed are the simple ones that restyle or hide parts of a page, which is exactly what Describe Extension does well. Anything that needs a server, an account or saved files is untouched.

For everyone else, our advice is to try it on one site first. Apple's guide explains how to restrict any extension's access from its toolbar button, but does not say whether a described extension starts with access to every website, so check before leaving it switched on.