WhichForecast

Download & install

WhichForecast is listed in the Microsoft Marketplace. The fastest path is Excel → Insert → Add-ins → search WhichForecast → Add. Works in Excel 2016, 2019, 2021, 2024 and Microsoft 365 (Windows & Mac) and Excel on the web.

Excel 2013 and 2010 are not supported — Microsoft's web add-in platform (Office.js) requires Excel 2016 or later.

In Excel — Insert tab, not File → Options. Open Insert → Add-ins (or Get Add-ins), search WhichForecast, then Add. The old File → Options → Add-ins → “Manage: Excel Add-ins” → Browse dialog only accepts legacy .xlam/.xll files and will not load WhichForecast.

Manual install (sideload)

Use this if the store is blocked in your organization, or you are on a perpetual Excel 2016 / 2019 / 2021 build that does not show the store. Download manifest.xml above, then follow the steps for your Excel.

If Excel says “Your add-in manifest is not valid”: open the downloaded file in Notepad. The first line must be <?xml version="1.0". If you see a web page instead, delete that file and use Download manifest.xml again. Then install via Insert → Add-ins → Upload My Add-in — not File → Options → Add-ins.

Which Excel are you using?

Excel on the web — easiest

  1. Open your workbook at excel.office.com.
  2. Insert → Add-ins → My Add-ins → Upload My Add-in.
  3. Click Browse…, choose manifest.xml, then Upload.
  4. A WhichForecast button appears on the Home tab. Select date + value columns → Forecast this selection.

Windows · Microsoft 365 / recent builds

  1. Insert tab → Add-ins (or More Add-ins).
  2. Open the My Add-ins tab, then click Upload My Add-in (top-right).
  3. Browse… to manifest.xml → Upload. WhichForecast appears on the Home tab.

No Upload My Add-in button? You have a perpetual build — switch to “Windows · 2021 / 2019 / 2016” above.

Windows · Office 2021 / 2019 / 2016 (perpetual)

No “Upload My Add-in” button — that’s expected. Use the Shared Folder catalog below.
  1. Put manifest.xml in a folder, e.g. C:\WhichForecast.
  2. Share the folder: right-click → Properties → Sharing → Share. You need the network path, e.g. \\YOUR-PC\WhichForecast — a local C:\… path will not work.
  3. Excel → File → Options → Trust Center → Trust Center Settings → Trusted Add-in Catalogs. Paste the \\ path, click Add catalog, tick Show in Menu, OK twice.
  4. Fully close and reopen Excel.
  5. Insert → My Add-ins → SHARED FOLDER tab → WhichForecast → Add.

Excel for Mac

  1. Copy manifest.xml into ~/Library/Containers/com.microsoft.Excel/Data/Documents/wef (create wef if needed).
  2. Restart Excel → Insert → My Add-ins → WhichForecast.
Use Google Sheets? WhichForecast is a Microsoft Office add-in (Office.js), so it doesn’t install in Google Sheets. Use it free in Excel on the web instead.

Developer sideload (from source)

pnpm install
pnpm --filter @whichforecast/forecast-engine build
pnpm dev:addin   # serves https://localhost:3000

# Then sideload apps/excel-addin/manifest.xml