How to Tell If a Website Uses Klaviyo

Klaviyo is the leading email and SMS marketing platform for ecommerce, the retention engine behind a huge number of direct-to-consumer brands. To tell whether a site uses it, the quickest answer is to look for the onsite script static.klaviyo.com/onsite/js/klaviyo.js?company_id=... — which even reveals the account's public company ID — or to type klaviyo into the console. This guide covers every reliable signal, the ecommerce-centric architecture behind them, and what a Klaviyo integration tells you about the business.

What is Klaviyo?

Klaviyo, founded in 2012, is a marketing-automation platform built specifically for ecommerce retention. Where Mailchimp is a general newsletter tool, Klaviyo is designed around store data: it integrates deeply with Shopify, BigCommerce, WooCommerce and Magento, ingesting product, order and behaviour events to power highly targeted email and SMS flows — abandoned cart, browse abandonment, post-purchase, win-back, and rich segmentation based on purchase history and predicted value. It has become the default retention platform for serious direct-to-consumer brands.

For detection, the key context is that Klaviyo is ecommerce-first and retention-focused. Finding it almost always means an online store that takes lifecycle marketing seriously — not a casual newsletter, but automated, data-driven flows tied to store events. That signals a growing or established DTC brand with real revenue and a retention strategy. Klaviyo's on-site footprint comes from its onsite tracking script (for forms, on-site behaviour and identification), which is consistent and reveals the account's public company ID.

How Klaviyo loads and tracks

A Klaviyo install loads the onsite script from https://static.klaviyo.com/onsite/js/klaviyo.js?company_id=XXXXXX (newer installs may reference klaviyo.js?company_id= via a slightly different path), where the company_id is the public six-character identifier of the Klaviyo account. This script powers Klaviyo's signup forms and pop-ups, on-site behaviour tracking (viewed product, started checkout) and visitor identification. It exposes a global klaviyo object (with methods like klaviyo.identify and klaviyo.track), and older installs use a _klOnsite/klOnsite array and the legacy _learnq queue.

Klaviyo sends tracked data and form submissions to its endpoints on a.klaviyo.com (the API) and fetch.klaviyo.com, and it sets a __kla_id cookie to persist the visitor's identity across sessions so behaviour can be tied to a profile. On ecommerce platforms, much of the order and product data flows server-side through Klaviyo's native integration, but the onsite script and __kla_id cookie remain visible in the browser. Knowing these — the klaviyo.js?company_id= script, the klaviyo global, the a.klaviyo.com/fetch.klaviyo.com endpoints, and the __kla_id cookie — makes Klaviyo straightforward to confirm.

How to tell if a website uses Klaviyo

Confirm at least one strong signal (the onsite script usually suffices).

1. View the source or Network tab. Search or filter for klaviyo. The onsite script static.klaviyo.com/onsite/js/klaviyo.js?company_id=XXXXXX is the definitive signal, and the company_id identifies the account.

2. Use the console. Type klaviyo and press Enter. A returned object (or the legacy _learnq array) confirms Klaviyo's onsite tracking is active.

3. Check cookies. Look for the __kla_id cookie, which Klaviyo sets to identify visitors.

4. Watch the Network tab. Calls to a.klaviyo.com or fetch.klaviyo.com (for tracking and form submissions) confirm live activity.

5. Read the company_id. The six-character company_id in the script URL identifies the specific Klaviyo account behind the site.

What the Klaviyo signals look like

<script async src="https://static.klaviyo.com/onsite/js/klaviyo.js?company_id=AbC123"></script>
window.klaviyo = { identify: ƒ, track: ƒ, … }   // or legacy _learnq = [...]
POST https://a.klaviyo.com/api/…    ;   GET https://fetch.klaviyo.com/…
Cookie: __kla_id = "…"

The combination of the klaviyo.js?company_id= script, the klaviyo global (or _learnq), and the __kla_id cookie is conclusive.

Klaviyo versus other email tools — avoiding false positives

Match the host to keep platforms distinct. Klaviyo uses static.klaviyo.com, a.klaviyo.com and a company_id; Mailchimp uses list-manage.com and chimpstatic.com; Omnisend (another ecommerce email tool) uses omnisrc.com/omnisend.com; ActiveCampaign uses *.activehosted.com. The company_id parameter and the klaviyo.js onsite script are unique to Klaviyo. Because Klaviyo is so tightly bound to ecommerce platforms, you will very often find it alongside Shopify; that pairing is expected, not a contradiction. The main subtlety is that some store data flows server-side, so the browser shows the onsite tracking but not the full event stream — the onsite script and __kla_id cookie are still conclusive.

How reliable is each Klaviyo signal?

The klaviyo.js?company_id= onsite script is definitive and reveals the account. The klaviyo global (or legacy _learnq) and the __kla_id cookie are equally strong. Calls to a.klaviyo.com/fetch.klaviyo.com confirm live tracking. The weakest situation is a store that relies mostly on Klaviyo's server-side integration with minimal onsite forms — even then, the onsite script and __kla_id cookie are usually present. As a rule, the onsite script or the __kla_id cookie settles it, and the company_id makes the finding account-specific.

What a Klaviyo integration reveals about a business

Finding Klaviyo is a strong signal of an ecommerce brand investing in retention and lifecycle marketing. Because Klaviyo is purpose-built for store-event-driven email and SMS, its presence implies automated flows (abandoned cart, post-purchase), segmentation, and a deliberate focus on repeat revenue — the hallmark of a serious DTC operation rather than a casual store. The near-certain pairing with an ecommerce platform (most often Shopify) tells you the business model at a glance. If you sell ecommerce services — retention strategy, SMS, reviews, loyalty, CRO, or complementary marketing tools — a Klaviyo store is an ideal-fit, revenue-generating prospect. A store running Klaviyo has already demonstrated willingness to pay for sophisticated marketing, which raises its value as a prospect.

What finding Klaviyo means for sales, agencies and competitive research

For sales and prospecting, Klaviyo is one of the highest-value ecommerce signals available: it marks a store with real revenue and a retention budget, exactly the profile that buys SMS, reviews, loyalty, subscription and CRO tools. Pairing a Klaviyo detection with the underlying ecommerce platform and other apps lets you size the brand and tailor the pitch precisely.

For agencies and consultants, finding Klaviyo tells you the client is already serious about lifecycle marketing, so the conversation moves to optimisation — better flows, segmentation, deliverability, SMS expansion — rather than convincing them email matters. It also signals budget and sophistication, justifying a higher-value engagement.

For competitive and market research, Klaviyo adoption across a set of DTC brands is a strong indicator of how mature retention marketing is in that niche. Spotting a competitor on Klaviyo (versus Mailchimp or a platform-native tool) tells you they likely run advanced flows, which is worth factoring into how you benchmark their customer lifecycle and lifetime value.

Klaviyo in the wider ecommerce stack

Klaviyo almost never appears alone — it is one piece of a recognisable direct-to-consumer stack, and mapping the rest adds enormous context. The near-certain companion is an ecommerce platform, most often Shopify, whose order and product events feed Klaviyo's flows; finding Shopify plus Klaviyo immediately tells you the business model and roughly the scale. Around that core you will frequently find a reviews tool (Yotpo, Okendo, Loox), a loyalty or subscriptions app, an SMS capability (Klaviyo's own or a specialist), and a CRO or pop-up tool — the classic retention-focused DTC toolkit.

The Klaviyo features in evidence refine the read further. On-site forms and pop-ups indicate active list growth; the presence of SMS consent fields suggests the brand runs SMS alongside email; and rich on-site tracking (viewed product, started checkout) signals sophisticated, behaviour-triggered flows. For an auditor, the valuable details are the underlying platform, the company_id, the reviews/loyalty/SMS apps present, and whether forms and SMS are in use; together these characterise a serious DTC brand and the maturity of its retention programme — far more actionable than the Klaviyo detection alone.

A quick Klaviyo confirmation walkthrough

Open the store with developer tools on the Network panel and filter for klaviyo. Look for static.klaviyo.com/onsite/js/klaviyo.js?company_id=... and note the company_id. Switch to the Console and type klaviyo (or check for _learnq) to confirm the onsite object. Open the Application panel and look for the __kla_id cookie. Watch for calls to a.klaviyo.com as you interact (especially viewing a product or starting checkout). The onsite script alone confirms Klaviyo and identifies the account.

A quick Klaviyo detection checklist

• Look for static.klaviyo.com/onsite/js/klaviyo.js?company_id=... — conclusive.
• Type klaviyo (or check _learnq) in the console.
• Check cookies for __kla_id.
• Watch the Network tab for a.klaviyo.com / fetch.klaviyo.com calls.
• Read the company_id to identify the account.
• Expect a pairing with Shopify or another ecommerce platform.

Detecting Klaviyo at scale

Checking one store is quick, but finding every Klaviyo brand across a list — to prospect retention-focused ecommerce — calls for automation. StackOptic detects Klaviyo and thousands of other technologies from a real browser, capturing the onsite script and the surrounding ecommerce stack. For related reading, see our guide to finding what email marketing platform a website uses and the full Klaviyo technology profile.