📅 August 2026 release notes

Newly available

The following features are newly available:

sibling-count() and sibling-index(): The sibling-count() and sibling-index() CSS functions return integers that are useful to style elements based on their positions among siblings or on the number of siblings, for example as part of a calc() expression.

The following features are now widely available:

Declarative shadow DOM: The shadowrootmode attribute on <template> creates a shadow root without the use of JavaScript. It is a declarative alternative to the attachShadow() method.

The following features are now available in Chrome:

Connection allowlists: The Connection-Allowlist HTTP response header limits which requests a page may initiate using fetch and other APIs.
Reference target: The referenceTarget property of a ShadowRoot object forwards attributes such as for and aria-labelledby to elements inside a shadow DOM. You can use this to, for example, link a <label> to its <input> even if the <input> is in the shadow DOM of a web component.
window-drag: The window-drag: move CSS declaration sets an element as a window drag handle, like a device's app title bar. You can use this to add click-and-drag areas to an installed progressive web app, often alongside window controls overlay.

The following features are now available in Chrome Android:

Connection allowlists: The Connection-Allowlist HTTP response header limits which requests a page may initiate using fetch and other APIs.
Reference target: The referenceTarget property of a ShadowRoot object forwards attributes such as for and aria-labelledby to elements inside a shadow DOM. You can use this to, for example, link a <label> to its <input> even if the <input> is in the shadow DOM of a web component.

The following features are now available in Edge:

Connection allowlists: The Connection-Allowlist HTTP response header limits which requests a page may initiate using fetch and other APIs.
Reference target: The referenceTarget property of a ShadowRoot object forwards attributes such as for and aria-labelledby to elements inside a shadow DOM. You can use this to, for example, link a <label> to its <input> even if the <input> is in the shadow DOM of a web component.
window-drag: The window-drag: move CSS declaration sets an element as a window drag handle, like a device's app title bar. You can use this to add click-and-drag areas to an installed progressive web app, often alongside window controls overlay.

The following features are now available in Firefox:

Iterator join(): The join() method of an Iterator object returns a string concatenation of all the iterator's items, separated by commas or a given separator string. It's similar to the join() method of arrays.

The following features are now available in Firefox for Android:

Iterator join(): The join() method of an Iterator object returns a string concatenation of all the iterator's items, separated by commas or a given separator string. It's similar to the join() method of arrays.