I would like to inject Custom css in modern site pages. Here i need to change all the fonts on the modern site and i would like to achieve this via App Customizer with SPFx Extensions. Any tips Or help ? Thanks in advance.

1 Answer 1


Check the demo shared by hugoabernier.

public onInit(): Promise<void> {
    Log.info(LOG_SOURCE, `Initialized ${strings.Title}`);

    const cssUrl: string = this.properties.cssurl;
    if (cssUrl) {
        // inject the style sheet
        const head: any = document.getElementsByTagName("head")[0] || document.documentElement;
        let customStyle: HTMLLinkElement = document.createElement("link");
        customStyle.href = cssUrl;
        customStyle.rel = "stylesheet";
        customStyle.type = "text/css";
        head.insertAdjacentElement("beforeEnd", customStyle);

    return Promise.resolve();

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.