SPFx 1.21.1 Ignoring externals Configuration — Bundling External Libraries Unexpectedly

[lhdeveloper]

Target SharePoint environment

SharePoint Online

What SharePoint development model, framework, SDK or API is this about?

💥 SharePoint Framework

Developer environment

macOS

What browser(s) / client(s) have you tested

• 💥 Internet Explorer
• 💥 Microsoft Edge
• 💥 Google Chrome
• 💥 FireFox
• 💥 Safari
• mobile (iOS/iPadOS)
• mobile (Android)
• not applicable
• other (enter in the "Additional environment details" area below)

Additional environment details

• browser version
• SPFx version: 1.21.1
• Node.js version 20.19.0

Expected Behavior

When defining libraries like moment, lodash, or others in the externals section of config/config.json, the final bundle should not include those libraries — reducing the overall bundle size. This was working correctly in SPFx 1.21.0.

Observed Behavior

After upgrading to SPFx 1.21.1, the same configuration is ignored, and external libraries (e.g., moment, lodash) are being bundled into the main JavaScript files, resulting in a massive increase in bundle size — from ~17MB to ~78MB — without any code changes.

Configuration

I have the following in config/config.json:

"externals": {
    "react": {
      "globalName": "React",
      "path": "https://cdn../libs/react.production.min.js"
    },
    "react-dom": {
      "globalName": "ReactDOM",
      "path": "https://cdn../libs/react-dom.production.min.js"
    },
    "moment": {
      "path": "https://cdn../libs/moment.min.js",
      "globalName": "moment"
    }
  },

[Ashlesha-MSFT]

Hello @lhdeveloper,
Thank you for bringing this issue to our attention. We will look into it and get back to you shortly.

[Ashlesha-MSFT]

@lhdeveloper,
I noticed that SPFx 1.21.1 officially requires Node.js version >=22.14.0 and <23.0.0, but you’re currently using Node 20.19.0, which might be causing compatibility issues. I saw some npm warnings about unsupported Node versions during install.. For reference, you can check the official compatibility guidelines here: https://learn.microsoft.com/en-us/sharepoint/dev/spfx/compatibility .

Regarding the issue you mentioned with externals being bundled unexpectedly in SPFx 1.21.1, I’ve already tested using Node 22.x with SPFx 1.21.1 on my side and wasn’t able to reproduce the problem. Could you try switching to Node.js 22.x and check if the issue still happens? Using the supported Node version might help avoid unexpected bundling behavior.

[lhdeveloper]

@Ashlesha-MSFT
Thank you for your feedback.

I had already tested with Node.js version 22.19.0 and experienced the same issue. However, after a more detailed analysis, I noticed that, following some optimizations I made to the gulpfile, the package size increased significantly for some reason.

Yesterday, I spent the whole day running more tests, and it seems that I managed to resolve the problem by adding a few rules to the gulpfile to ensure it compiles correctly.

I believe the issue is now resolved, so we can close this ticket. If I encounter any related issues in the future, I'll comment here again.

Thanks again!