SPFX Very slow on mobile devices / iFrame Sharepoint

Target SharePoint environment

SharePoint Online

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

💥 SharePoint Framework

Developer environment

Windows

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

• Tried SPFx version : 1.15, 1.16, 1.23
• Tried Node.js version : 16.13.2, 18.20.4, 25.1.0

Describe the bug / error

Issue: Extremely Slow iFrame Loading from SPFx Modules on Mobile Devices

Category

Performance / SPFx / iFrame / Mobile

Devices affected: Mobile devices (smartphones, tablets)

Date issue started: May 2025

Additional Notes

The slowdowns began around May.

The iFrame loads SharePoint Online pages.

By default, we have a static tab that looks like this:

"staticTabs": [
  {
    "entityId": "teams-myapp-dev",
    "name": "Teams - MyApp",
    "websiteUrl": "https://{teamSiteDomain}",
    "contentUrl": "https://{teamSiteDomain}/_layouts/15/TeamsLogon.aspx?SPFX=true&dest=/_layouts/15/teamshostedapp.aspx?teams%26personal%26componentId=<COMPONENT-ID>%26forceLocale={locale}",
    "scopes": [
      "personal"
    ]
  }
]

And our TypeScript code looks like this:

public render(): void {
  if (this.context.sdks.microsoftTeams) {

    this.context.sdks.microsoftTeams.teamsJs.app.getContext().then(context => {
      const language = context.app.locale;
      let page: string = Constants.EnglishUrl;
      if (language.indexOf('fr') === 0) {
        page = Constants.FrenchUrl;
      }

      this.domElement.innerHTML = `<iframe width='100%' height='100%' src=${page} />`;
      this.domElement.parentElement.style.overflow = 'hidden';
    }, err => {
      console.error(err);
    });
  } else {
    this.domElement.innerHTML = '';
  }
}

No changes were made between the time when it worked correctly and the moment it stopped working.

We suspect a regression or platform-side performance issue.

Has anyone else experienced this behavior?
Any known fixes, workarounds, or updates from Microsoft?

Thanks!

Steps to reproduce

• Create or use an existing SPFx web part containing an iFrame loading a SharePoint page.
• Load the page on a mobile device.
• Observe that the iFrame takes significantly longer to load than expected.

Expected behavior

Pages loaded inside an iFrame from an SPFx web part should load at normal speed on mobile devices, comparable to desktop performance.

Observed Behavior

Since May, pages embedded in an iFrame from our SPFx modules load extremely slowly on mobile terminals.
The issue does not appear (or appears far less) on desktop browsers.