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Customizing Klaviyo Modal Styling in Shopify

If you're like me, you may have found that customizing the styling of a Klaviyo modal within a Shopify store can be a real headache. This is mainly due to the modal being contained within an iframe, which can limit styling capabilities. However, after much trial and error, I've found a way to update the styling and make my Klaviyo modal fit my store's aesthetic more seamlessly. In this blog post, I'll walk you through the process step by step.

Importing a CSS File for Additional Styles

Klaviyo allows you to import a separate file containing additional styles. This is a game-changer, as it empowers you to make essential stylistic changes to your modal. To do this, we’ll need to update the additional_styles parameter within the relevant code.

This here is the Original Back in Stock code from Klaviyo at

Original Klaviyo BIS Code

Here is an example of how to add the additional_styles parameter within a typical script in Shopify:

Updated with Klaviyo-bis-modal.css

This code leverages a Shopify-specific aspect to import your CSS file. Once you've added the parameter, the next step is to create the actual CSS file and add your desired styling updates.

Creating the CSS File and Customizing Modal Styles

In this step, you'll be creating a new CSS file within your Shopify store that will house your custom Klaviyo modal styles.

  1. Within your Shopify admin, go to your theme's files by navigating to Online Store > Themes > Actions > Edit code.
  2. Add a new asset by clicking on the Add a new asset button, and then select the Create a blank file option.
  3. Name your file, for example: klaviyo-bis-modal.css, and click the Create asset button.
  4. Open the newly created file, and start adding your custom styles. Remember to target the elements within the Klaviyo modal.

Here's an example of how to update the modal title color:

CSS to override modal Title in Klaviyo Bis Modal

By including your custom styles within a specific class (in this case, #klaviyo-bis-modal), you can ensure that these changes won't cascade outside the Klaviyo modal.

Testing Your Updated Klaviyo Styling

With your updated styles in place, you can now test to see if your changes have taken effect. Visit your Shopify store and trigger the Klaviyo modal (usually done by subscribing to a newsletter or engaging with a specific call-to-action).

If everything has been set up correctly, you should see your custom styles applied to the modal. In the example above, the modal title should now be blue.

Blue Title in BIS Modal from Css file


Updating the styling of a Klaviyo modal within Shopify might initially seem impossible due to the modal being contained within an iframe. Nonetheless, by importing a separate CSS file and housing your custom styles within it, you can easily make the desired changes.

While the process isn't entirely straightforward, following these steps will allow you to take control and have your Klaviyo modal reflect your store's branding more accurately.

If you still aren't sure on how to custom style the Klaviyo Bis Modal. Please feel free to reach out. We would be more than happy to help you Customize your BIS Modal!

Happy customizing!

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