Safari Technology Preview 248 puts JavaScript and accessibility changes on the test bench

WebKit made Safari Technology Preview 248 available on July 22, 2026, for macOS Golden Gate and macOS Tahoe. This report looks at what selected changes mean for website teams planning their browser tests.

A preview for earlier comparisons

Technology Preview is a separate application that can run alongside Safari. It provides a way to examine WebKit during development and give feedback before changes reach the stable browser.

A team could open the same page in stable Safari and the preview, using identical files, steps and expected results. Keeping those conditions consistent makes the comparison repeatable.

If a problem appears in one environment, gradually reducing the page to a smaller example can help isolate it. The resulting case gives developers a clearer way to investigate their code and the browser’s behavior.

Recording the actions preceding a problem matters too. A page immediately after loading may behave differently from the same page after interaction or after returning from another page.

BigInt Math reaches the preview

Release 248 adds support for the BigInt Math proposal, including BigInt.pow and BigInt.sqrt. It also adds the no-clamp option to CSS progress().

For an application team, a useful question is which path runs when a feature is available and which alternative runs when it is absent. Covering both makes it possible to assess whether users can complete their task in either environment.

An informative test connects the feature with an observable result. The team can check that an operation completes and produces the expected output, then repeat the exercise through its alternative path.

Visible content must also be reachable

An accessibility correction concerns content using hidden="until-found". WebKit’s change and accompanying regression test check that revealed content becomes reachable to assistive technology, then becomes unreachable again when it is hidden.

A website team could apply that idea to an expandable questions-and-answers section. The test would examine the visible text, focus position and a screen reader’s ability to reach the content.

Running a complete cycle—opening, closing and reopening the section—provides a more representative exercise than reviewing a static view of the page.

Writing down the expected result at each step also makes a discrepancy easier to describe. A small reproducible example can then support a clearer bug report.

Release 248 gives teams an opportunity to find differences early. Its practical value comes from the user journeys tested and the problems documented, while the preview remains a separate stage from delivery in stable Safari.

Sources

• WebKit — Release 248, 22 July 2026
• WebKit — accessibility fix and regression test
• WebKit — Technology Preview background