SharePoint Document Issues

How to Customize a SharePoint Modern Page with HTML, JavaScript, or CSS

Maira Mehtab Sep 27, 2026 869 views

Question details

The user wants to inject custom HTML, JavaScript, or CSS into an entire SharePoint modern page instead of modifying individual SPFx web parts.

Product: SharePoint
Device & OS: not provided
Scenario: Customizing the appearance and behavior of a modern SharePoint page with custom code snippets.
Observed behavior: To successfully deploy, configure, and troubleshoot the third-party Modern Script Editor web part to run the custom scripts on the page.

Before you start

Ensure you have the necessary SharePoint administrative permissions to deploy custom apps to the App Catalog and add web parts to your modern pages.

Solution 1Recommended

Use the Modern Script Editor Web Part

Install and use the third-party Modern Script Editor to inject custom HTML, CSS, and JavaScript into your modern page.

By default, SharePoint modern pages do not include a native script editor. The Modern Script Editor is a popular community-driven tool from the SharePoint Patterns and Practices (PnP) community that allows you to easily embed custom scripts onto these pages.

Deploy the Web Part Package

Download the Modern Script Editor app package from the official PnP GitHub repository and upload it to your SharePoint App Catalog.

Add to Your Modern Page

Navigate to the modern page you want to customize, click 'Edit' in the top right corner, and click the '+' icon to add a new web part. Search for 'Modern Script Editor' and add it to the page.

Inject Custom Code

Click the 'Edit snippet' button inside the newly added web part and paste your HTML, JavaScript, or CSS code into the editor. Save and publish the page.

Not a Microsoft Product: The Modern Script Editor is an open-source solution and is not officially supported by Microsoft. Ensure your organization's security policies permit third-party scripts.

Solution 2

Troubleshoot Modern Script Editor Issues

Resolve issues if the Modern Script Editor web part fails to load or execute your custom code.

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Frequently Asked Questions

Is the Modern Script Editor an official Microsoft product?

No, the Modern Script Editor is a third-party open-source web part developed by the SharePoint Patterns and Practices (PnP) community. It is not officially supported by Microsoft.

Can I use standard SPFx web parts instead of the Modern Script Editor?

Yes, standard SharePoint Framework (SPFx) web parts are the officially recommended way to add custom functionality. However, the Modern Script Editor is often preferred for quick injections of HTML, CSS, or JavaScript without having to write, build, and deploy custom SPFx code from scratch.

Why is my JavaScript not executing on the modern page?

By default, SharePoint modern pages restrict custom script injection for security reasons. Ensure that your tenant allows custom scripts, that the Modern Script Editor web part is correctly deployed, and that you are using the latest version of the app.

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