AIBRIEF
The in cell AI formula was a Microsoft 365 Insider / Frontier early access preview that never reached general availability; the Copilot side pane, Copilot agents, and the broader Microsoft 365 Copilot subscription remain available.
Microsoft is retiring Excel's =COPILOT() worksheet function on 2026-09-14, ending the only in-cell way to invoke its Copilot AI before the feature reached general availability. The retirement, announced in Microsoft 365 Message Center notice MC1454373 on 2026-08-14, applies to the in-cell function only. The Copilot side pane, Copilot agents, and the broader Microsoft 365 Copilot subscription all remain available.
The function, documented on Microsoft's support site, was a preview gated to the Excel Frontier and Microsoft 365 Insider programs and required a Microsoft 365 Copilot license (work/school) or Microsoft 365 Premium (individuals). Use cases Microsoft itself listed included summarizing text, generating sample data, classifying sentiment across a range, and web lookups. Microsoft's own guardrails restricted it: not for numerical calculation, not for XLOOKUP-style lookups, capped at 100 calls per 10 minutes, and blocked in workbooks labelled Confidential or Highly Confidential.
After 2026-09-14, users can no longer create new =COPILOT() formulas, and existing workbooks that reference it are expected to break rather than fall back. Microsoft framed the move as streamlining the Copilot experience by consolidating two entry points into one. No independent adoption, usage, or developer reaction data has been published.