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Answer
Should I use an HTML embed or site-wide custom code?
Short answer
Use site-wide custom code for an install popup, analytics or other scripts that need to run with the page. Use an HTML embed for a form, map or widget displayed in one spot. Many builders render HTML embeds inside iframes, which isolates them from the main page.
By InstantPWA engineering·Reviewed October 22, 2026
Why iframes matter
An iframe is a separate document. Code inside it can render inside its own box, but it does not become part of the page’s main layout or document.
Signs you picked the wrong one
The popup appears only inside a small box, does not appear on other pages, or the installation check cannot find the script in the published page.
Where to look
Search the builder’s settings for Custom Code, Code Injection, Header and Footer, or Theme Code. Body-end placement is a good default for a deferred script.
Setup guides for your website
Related
Why is my Wix custom code not working?
Wix custom code commonly fails when it is tested in the editor, added through an HTML iframe, limited to the wrong page, or used before the site is published on a connected domain. Add it in Settings → Custom Code, choose All pages, load it once, place it at Body-end and test the live domain.
Why is my Carrd custom code not working?
Carrd custom code usually fails because the site is not on Pro Standard or higher, the code was added as an iframe instead of a hidden Code embed, the site was not republished, or you are testing an editor preview. Use a hidden Code embed at Body End and check the exact published address.
How do I check if a script is installed on my website?
Open the published website, not the editor, then view its source and search for the script address or ID. In developer tools, check Network for the script request and Console for errors. Use the exact domain visitors use; www, subdomains and custom domains can be different sites.
Can I add a service worker to a website builder?
Only if the builder lets you serve a JavaScript service worker from the same origin as your site. A script from another domain can add a popup, but it cannot register an outside worker to control your pages. Without that file, offline caching and full PWA behaviour need a different hosting setup.
Is an install popup the same as a PWA?
No. An install popup is guidance that helps visitors add your website to their home screen. A full PWA uses a web app manifest and service worker so supported browsers can treat it as an installable app, with optional offline caching and push. A popup can be useful without promising every PWA feature.
What is a PWA?
A PWA (Progressive Web App) is a regular website that meets three technical criteria — HTTPS, a Web App Manifest and a service worker — so browsers let visitors install it on their home screen. Once installed, it launches like a native app, works offline and can send push notifications.