For brands using a fast, content-driven Gatsby site, connecting Klaviyo can turn anonymous visits into measurable email and SMS marketing opportunities. A Klaviyo and Gatsby integration typically focuses on three goals: capturing subscribers, tracking behavior, and syncing ecommerce or lead data into meaningful Klaviyo profiles. Because Gatsby renders pages differently from traditional server-side websites, the integration should be planned carefully to avoid script loading issues, hydration errors, and incomplete analytics.

TLDR: A Gatsby site can integrate with Klaviyo through embedded signup forms, custom API-based forms, and client-side tracking scripts. The safest approach is to load Klaviyo only in the browser, keep public keys in environment variables, and test events in Klaviyo before launching. For ecommerce stores, product views, cart actions, and checkout events should be mapped clearly so Klaviyo flows and segments work correctly.

Understanding the Integration

Klaviyo is designed to collect customer data and use it for email marketing, SMS campaigns, segmentation, automation, and personalization. Gatsby, on the other hand, is a React-based framework commonly used for static sites, headless commerce storefronts, blogs, and landing pages. The main challenge is that Gatsby builds pages ahead of time, while Klaviyo tracking depends on browser-based activity.

That means Klaviyo scripts should generally be loaded client-side, not during Gatsby’s build process. Any code that references window, document, or browser cookies must be protected so it does not run during server-side rendering.

Common Integration Methods

There are three common ways a Gatsby site can use Klaviyo:

• Embedded Klaviyo forms: The fastest option for newsletter popups, flyouts, and inline forms.
• Custom signup forms: Ideal when the site needs full design control or a headless user experience.
• Behavioral tracking: Used for tracking page views, product views, add-to-cart events, and identified users.

For many sites, a combination works best. A simple blog may only need an embedded form, while a Gatsby ecommerce storefront may need custom events, user identification, and product catalog data.

Step 1: Prepare Klaviyo

Before any code is added to Gatsby, the Klaviyo account should be configured. The site owner should create or confirm the correct list for subscribers, locate the public API key, and decide which events need to be tracked. The public API key is safe for browser usage, but private API keys should never be exposed in Gatsby frontend code.

Useful preparation steps include:

1. Create a dedicated subscriber list, such as Newsletter Subscribers.
2. Find the Klaviyo public API key in the account settings.
3. Define core events, such as Viewed Product, Added to Cart, or Submitted Form.
4. Check whether consent is needed for email, SMS, cookies, or tracking scripts.

Step 2: Add Environment Variables in Gatsby

Gatsby supports environment variables, but only variables prefixed with GATSBY_ are exposed to browser code. A project may include a value such as:

GATSBY_KLAVIYO_PUBLIC_KEY=PUBLIC_KEY_HERE

This value can then be referenced in the Gatsby application. Private keys should be kept on a backend, serverless function, or secure middleware layer if API calls require authentication.

Step 3: Load the Klaviyo Script Safely

Klaviyo’s onsite tracking script can be added in Gatsby using gatsby-browser.js, a React layout component, or a dedicated script management approach. The key rule is to load it only in the browser. A Gatsby developer should avoid running Klaviyo code during the build.

A typical browser-only script injection pattern checks whether window exists before appending the script. This prevents build errors and keeps Gatsby’s static rendering process clean. If the site uses a consent management platform, the Klaviyo script may need to load only after the visitor grants permission.

Step 4: Add Signup Forms

The easiest form integration is Klaviyo’s native embedded form. Klaviyo provides a form ID and embed snippet, which can be placed inside a Gatsby component. This method is useful for marketers because form design, targeting, and behavior can be managed directly in Klaviyo.

However, custom forms may be better when the Gatsby site has a highly specific design system. In that case, the form can collect an email address and submit it to Klaviyo through an approved endpoint or backend function. This approach provides greater control over validation, styling, success messages, and multi-step lead capture.

When building forms, the site should include clear consent language. If SMS is collected, the compliance requirements are usually stricter than email, and the form should clearly explain what the subscriber is agreeing to receive.

Step 5: Identify Visitors

Klaviyo becomes more powerful when it can connect behavior to known profiles. Once a visitor submits a form, logs in, or completes checkout, the Gatsby site can identify that person by email. Future tracked events can then appear on the correct Klaviyo profile.

This identification step is important because anonymous page activity has limited marketing value. Once linked to a profile, events can trigger flows such as welcome series, browse abandonment, cart reminders, post-purchase education, and win-back campaigns.

Step 6: Track Ecommerce Events

For Gatsby storefronts, event tracking should be mapped before implementation. The development team should define what data each event includes and ensure the naming matches Klaviyo’s expectations where possible.

• Viewed Product: Product name, image, URL, price, SKU, and category.
• Added to Cart: Product details, quantity, cart value, and checkout URL.
• Started Checkout: Cart contents, total value, and customer email if available.
• Placed Order: Usually sent from the ecommerce platform or backend, not only from Gatsby.

Client-side events are helpful, but order-related events should be handled carefully. Since browser events can be blocked or interrupted, important purchase data is often more reliable when sent from the ecommerce platform, backend, or serverless function.

Step 7: Test the Integration

After the integration is implemented, testing should confirm that subscribers are added to the correct list, profiles are created or updated, and events appear with the expected properties. Klaviyo’s profile activity timeline is useful for checking whether the integration is working.

The testing process should include:

• Submitting a test email through each form.
• Checking whether consent status is recorded correctly.
• Viewing a product and confirming the event appears in Klaviyo.
• Adding an item to cart and validating event properties.
• Testing production builds, not only local development.

Best Practices

A strong Klaviyo and Gatsby integration balances performance, privacy, and marketing usefulness. Scripts should not slow down the main page experience, and form loading should not cause layout shifts. Gatsby’s speed is often a major reason for using the framework, so marketing scripts should be added thoughtfully.

Recommended best practices include:

• Load scripts asynchronously to protect page performance.
• Use environment variables for public configuration values.
• Keep private API keys off the frontend at all times.
• Respect cookie and marketing consent based on the visitor’s region.
• Standardize event names so flows, reports, and segments remain clean.
• Monitor data quality after launch to catch missing or duplicated events.

FAQ

Can Klaviyo be used with Gatsby?

Yes. Klaviyo can be integrated with Gatsby through embedded forms, client-side tracking scripts, and custom API-based workflows. The main requirement is that browser-specific code must run only on the client side.

Where should the Klaviyo script be added in Gatsby?

It can be added through gatsby-browser.js, a layout component, or a script management component. The implementation should check for browser availability before referencing window or document.

Is a private Klaviyo API key safe in Gatsby?

No. Gatsby frontend code is visible in the browser, so private API keys should never be included there. Sensitive requests should go through a backend or serverless function.

Should signup forms be embedded or custom built?

Embedded forms are faster to launch and easier for marketers to manage. Custom forms are better when the site requires full control over design, validation, or user experience.

Why are Klaviyo events not appearing?

Common causes include blocked scripts, missing consent, incorrect public keys, browser-only code running during build, or event payload errors. Testing in the Klaviyo profile timeline can help identify the issue.