The includeShadowRoots argument was a never-standardized argument to the DOMParser.parseFromString() function, which was there to allow imperative parsing of HTML content that contains declarative shadow DOM. This was shipped in M90 [1] as part of the initial shipment of declarative shadow DOM. Since the standards discussion rematerialized in 2023, the shape of DSD APIs changed, including this feature for imperative parsing. (See [2] for more context on the standards situation and recent changes, and see [3] and [4] for other related deprecations.) Now that a standardized version of this API, in the form of setHTMLUnsafe() and parseHTMLUnsafe() will ship in Chrome 124 ([5]), the non-standard includeShadowRoots argument needs to be deprecated and removed. All usage should shift accordingly: Instead of: (new DOMParser()).parseFromString(html,'text/html',{includeShadowRoots: true}); this can be used instead: document.parseHTMLUnsafe(html); [1] https://chromestatus.com/feature/5191745052606464 [2] https://chromestatus.com/feature/5161240576393216 [3] https://chromestatus.com/feature/5081733588582400 [4] https://chromestatus.com/feature/6239658726391808 [5] https://chromestatus.com/feature/6560361081995264
Now that there is a standardized version of this API, it makes sense to remove the non-standard, Chrome-only version of the API.