silentship
lowprodbeta

OfficeCore.RibbonButton: 4 API changes in Office.js (undocumented API)

UndocumentedNot in Microsoft's documentation

OfficeCore.RibbonButton, not in Microsoft's documentation, set implementation changed on the Office.js production CDN in 16.0.20626.15200, first seen 2 Nov 2026, 22:50 UTC. Affects Excel on iOS, Mac, web, Windows and Android, PowerPoint on iOS and web, Visio on Windows, Word on iOS, Windows and web and OneNote on Mac, Windows and Windows (WinRT).

Production
actionId added in 16.0.20626.15200, first seen 2 Nov 2026, 22:50 UTC; rolling out, on 2% of sampled edges.
Beta
actionId added in 16.0.20626.15200, first seen 2 Nov 2026, 22:20 UTC; rolling out, on 1% of sampled edges.

What this means for your add-in

Same name and signature, different implementation: behaviour can differ even though the API surface did not change.

It is not in Microsoft's documentation (neither @types/office-js nor @types/office-js-preview): an internal API that can change in any build. Do not depend on it; if you must, check that it exists before use — if (OfficeCore.RibbonButton) { … }.

Change history

Change
Build
Severity
Hosts
actionId added
property undocumented
16.0.20626.15200
prod 2 Nov 2026, 22:50 UTC
Rolling out · 2%
low
Excel on iOSExcel on MacExcel on webExcel on WindowsPowerPoint on iOSVisio on WindowsWord on iOSWord on Windows
icon added
property undocumented
16.0.20626.15200
prod 2 Nov 2026, 22:50 UTC
Rolling out · 2%
low
Excel on iOSExcel on MacExcel on webExcel on WindowsPowerPoint on iOSVisio on WindowsWord on iOSWord on Windows
set implementation changed
undocumented
16.0.20626.15200
prod 2 Nov 2026, 22:50 UTC
Rolling out · 2%
low
Excel on iOSExcel on MacExcel on webExcel on WindowsPowerPoint on iOSVisio on WindowsWord on iOSWord on Windows
toJSON implementation changed
undocumented
16.0.20626.15200
prod 2 Nov 2026, 22:50 UTC
Rolling out · 2%
low
Excel on iOSExcel on MacExcel on webExcel on WindowsPowerPoint on iOSVisio on WindowsWord on iOSWord on Windows
actionId added
property undocumented
16.0.20626.15200
beta 2 Nov 2026, 22:20 UTC
Rolling out · 1%
low
Excel on AndroidExcel on MacOneNote on MacOneNote on WindowsOneNote on Windows (WinRT)PowerPoint on webWord on iOSWord on web
icon added
property undocumented
16.0.20626.15200
beta 2 Nov 2026, 22:20 UTC
Rolling out · 1%
low
Excel on AndroidExcel on MacOneNote on MacOneNote on WindowsOneNote on Windows (WinRT)PowerPoint on webWord on iOSWord on web
set implementation changed
undocumented
16.0.20626.15200
beta 2 Nov 2026, 22:20 UTC
Rolling out · 1%
low
Excel on AndroidExcel on MacOneNote on MacOneNote on WindowsOneNote on Windows (WinRT)PowerPoint on webWord on iOSWord on web
toJSON implementation changed
undocumented
16.0.20626.15200
beta 2 Nov 2026, 22:20 UTC
Rolling out · 1%
low
Excel on AndroidExcel on MacOneNote on MacOneNote on WindowsOneNote on Windows (WinRT)PowerPoint on webWord on iOSWord on web

Changed in the same rollouts

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 OfficeCore.RibbonButton; 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). OfficeCore.RibbonButton is not in Microsoft's documentation.