Word.LineFormat: 10 API changes in Office.js
GA · WordApiDesktop 1.3Microsoft's documentation
Word.LineFormat, a generally available API (WordApiDesktop 1.3), backgroundColor removed on the Office.js production CDN in 16.0.20619.15190, first seen 26 Oct 2026, 18:50 UTC. Affects Word on web and iOS.
- Production
- backgroundColor removed in 16.0.20619.15190, first seen 26 Oct 2026, 18:50 UTC; rolling out, on 4% of sampled edges.
- Beta
- backgroundColor removed in 16.0.20619.15190, first seen 26 Oct 2026, 19:00 UTC; rolling out, on 5% of sampled edges.
What this means for your add-in
On clients that load the new build, Word.LineFormat.backgroundColor is undefined: calling or constructing it throws a TypeError (the messages are below).
It is a generally available API (WordApiDesktop 1.3), so its requirement-set check still passes after this change. Check the API itself before use — if (Word.LineFormat) { … } — and report the removal to Microsoft (OfficeDev/office-js on GitHub).
Errors you may see
In the add-in's console or error logs, on clients that loaded the new build. Parts in <…> come from your own code.
TypeError: <object>.backgroundColor is not a functionWindows, web, Android (Chromium)TypeError: <object>.backgroundColor is not a function. (In '<object>.backgroundColor(…)', '<object>.backgroundColor' is undefined)Mac, iOS (Safari)
Change history
Changed in the same rollouts
- OfficeCore.FlightingService added
- OneNote.ServiceId enum values
Source
silentship samples every Office.js file on the CDN every 10 minutes and compares the public API surface of each new build with the previous one by reflection. This page lists what changed for Word.LineFormat; it does not include Microsoft's code. The API status comes from Microsoft's published type definitions (@types/office-js and @types/office-js-preview). Documentation: Word.LineFormat on Microsoft Learn.