Microsoft is retiring Excel's COPILOT() function
Microsoft is withdrawing the in-cell COPILOT() function on
14 September 2026, about a year after it appeared. It never left preview
— it shipped to the Frontier programme and is going before a full public launch — and
Microsoft's stated reason is consolidation: the Copilot experience already inside Excel is
the better place for it. If you use =COPILOT() to have a formula explained,
this is what changes and what to do instead.
What actually goes away
Only the in-cell function. The Copilot side pane remains, and Microsoft directs you there. The practical difference is bigger than it sounds. A function lives in a cell, next to the thing it is talking about, and its answer stays put where you can read it beside the formula. A pane is a conversation you have to keep re-having.
The second difference matters more: the side pane needs a paid Microsoft 365 Copilot licence. The number of people who inherit a spreadsheet they did not build is very much larger than the number holding a Copilot seat, and the gap is widest exactly where inherited models hurt most — small firms, accountancy practices, engineering consultancies, charities.
What you can still do, with nothing installed
Most of the work of understanding a formula is not the syntax. It is finding out that
Data!$F$2:$F$800 is the Net amount column, that the 1.08
is an uplift typed into forty other formulas, and that the row above uses a different
pattern. Excel will tell you all three if you ask it in the right order:
- Select part of a formula in the formula bar and press F9. Excel replaces the selection with what it evaluates to. Press Escape, not Enter — Enter commits the evaluated value over your formula and destroys it.
- Formulas › Trace Precedents draws arrows to what a cell reads. Double-click an arrow to jump.
- Ctrl + ` (the backtick, top-left of the keyboard) shows every formula on the sheet at once, which is the fastest way to see that one cell in a column is different.
- Formulas › Evaluate Formula steps through a calculation one operation at a time.
None of that needs a licence, an add-in, or an internet connection. It is slow on a big model, which is the honest case for tooling — not that Excel cannot tell you, but that it tells you one keystroke at a time.
Where this add-in fits
Formula Explainer does the reading-in-order part automatically: select a cell and it says what the formula does in the workbook's own words — the real column headers, the defined names, the live values, and what will break it. It is not a Copilot replacement and does not pretend to be: it explains formulas, it does not write them, and it has no AI in it at all. Nothing is sent anywhere; the whole explanation is worked out in the pane.
That is also why explaining is free, permanently, with no metering and no account — every cell, every workbook. There is no per-question cost to pass on, because there is no model and no API call behind it. What costs money is documenting a whole model at once, which is a different job.
If you have =COPILOT() in a workbook
Those cells stop doing what they do. Microsoft's guidance is to remove or replace them before the retirement date, and because the function was never generally available there is no supported in-cell successor to swap in. The fix is to work out what each one was for and rebuild it — which nearly always means reading the surrounding model first.
That is the same problem as inheriting somebody else's spreadsheet, and there is a method for it: how to take over someone else's spreadsheet, in ten steps, all of them doable with nothing but Excel.