Email is the highest-ROI marketing channel for most companies, which means the platform they choose is a real investment — not just a line item. Klaviyo signals a serious e-commerce operation. Mailchimp often means a small team keeping costs low. ActiveCampaign suggests a content or SaaS business with a nurture-heavy funnel. Brevo (formerly Sendinblue) typically indicates a European company or one optimizing for price. Each choice implies something.
The practical reasons to know this are varied: you might be selling marketing services and want to understand your prospect's current stack, evaluating whether a competitor is investing in lifecycle marketing, or benchmarking your own platform choice against similar companies. Whatever the reason, identifying what email marketing software a company uses is almost always doable from browser signals alone.
The Fastest Method: One-Click Detection
SaaS Detective is the most direct path — it's a free Chrome extension that automatically detects email marketing tools (and 200+ other technologies) when you open the popup on any page. It identifies Klaviyo, Mailchimp, ActiveCampaign, ConvertKit, Drip, Brevo, GetResponse, and more by their JavaScript signatures, without requiring you to dig through source code.
For manual detection, the methods below are reliable and require nothing but a browser.
Signal 1: Subscribe Forms and Embedded Scripts
The most consistent signal is the subscription form a company embeds on their site. Every major email platform generates a unique embed code, and the JavaScript or iframe it loads identifies the provider:
- Klaviyo — forms load from
a.klaviyo.com, and the page source containsklaviyo.jsor a_learnqJavaScript object - Mailchimp — embedded forms load from
list-manage.com; their pop-up forms usechimpstatic.com; themc-embedded-subscribe-formclass appears in form HTML - ActiveCampaign — forms are embedded from
activehosted.com; their tracking script loads fromtrackcmp.net - ConvertKit — forms use
f.convertkit.comas the action URL; their subscriber scripts load fromassets.convertkit.com - Drip — tracking script loads from
dc.krxd.netorcdn.getdrip.com - Brevo — formerly Sendinblue; look for
js.brevo.comor form actions pointing tosendinblue.com - GetResponse — forms embed from
app.getresponse.comor use their webform JavaScript atgy-mail.com - Beehiiv — newsletter embeds load from
subscribe-forms.beehiiv.com, very distinctive iframe format - Substack — embed iframes come from
substack.com/embed
To see these, right-click the page and select "View Page Source" (Ctrl+U), then search for the platform names or the domain patterns above. The subscribe or newsletter section of any site is the most reliable place to look — that's where the email form lives.
Signal 2: Pop-Up and Exit-Intent Scripts
Many email marketing platforms offer built-in pop-up builders. When a company uses these, the pop-up JavaScript loads from the platform's CDN before you even interact with the page:
- Klaviyo — their pop-up builder is native; you'll see
klaviyo.jsload on page entry - Mailchimp — pop-ups load from
chimpstatic.com - Privy (a Klaviyo-adjacent tool) — scripts load from
widget.privy.com - OptinMonster — scripts load from
a.opmnstr.com
Open Chrome DevTools (F12), go to the Network tab, filter by JS, and reload the page. Look at what loads in the first 2 seconds — email platform scripts almost always load early since they need to be ready before the user scrolls to the form or triggers a pop-up.
Signal 3: SPF and DNS Records
Email platforms send emails on behalf of companies, which requires them to be listed in the domain's SPF record. These records are public and searchable. Use any free DNS lookup tool and look at the TXT records for the company's domain:
include:servers.mcsv.net→ Mailchimpinclude:email.klaviyo.comor_spf.klaviyo.com→ Klaviyoinclude:spf.sendinblue.com→ Brevo / Sendinblueinclude:_spf.activehosted.com→ ActiveCampaigninclude:spf.getresponse.com→ GetResponseinclude:spf.convertkit.com→ ConvertKit / Kitinclude:amazonses.com→ Amazon SES (often means a custom email setup or a developer-focused tool like Customer.io or Postmark)
This method is particularly useful for companies that don't show their email platform on their website — maybe they don't have a public subscribe form, or they've loaded their forms through a tag manager that obscures the source. The DNS record doesn't lie: if Klaviyo is in their SPF, Klaviyo is sending their email.
Start with SaaS Detective on the company's homepage and newsletter/subscribe page. If that doesn't reveal it, check their DNS SPF record via any free DNS lookup tool. For e-commerce companies, navigate to their product pages and checkout — Klaviyo often loads additional tracking scripts there that aren't present on marketing pages.
Signal 4: Unsubscribe Links and Email Headers
If you've received a marketing email from the company — or can sign up for their list — the email itself is the most definitive signal. Every email marketing platform injects its own unsubscribe infrastructure:
- Klaviyo — unsubscribe links contain
klaviyomail.comoremail.klaviyo.com - Mailchimp —
list-manage.comappears in unsubscribe and footer links - ActiveCampaign — tracking links go through
[subdomain].activehosted.com - ConvertKit — unsubscribe links use
convertkit.comorck.page - Beehiiv — emails route through
beehiiv.comdomains
Looking at the email headers ("View Original" or "Show Original" in Gmail) reveals even more: the Return-Path, X-Mailer, and Message-ID headers often include the sending platform's domain. This is bulletproof identification — there's no ambiguity when the headers say who sent it.
What Email Platform Choice Tells You
Email tool selection correlates strongly with business type and sophistication:
- Klaviyo — almost certainly e-commerce, serious about email revenue, likely doing segmentation and automated flows, revenue above mid-six figures minimum
- Mailchimp — small business or early-stage startup, value-conscious, probably not doing sophisticated automation
- ActiveCampaign — SaaS, content business, or service company with a complex lead nurture sequence, CRM-like usage of email
- ConvertKit / Kit — creator economy — blogger, newsletter writer, course creator, or indie maker
- Brevo — often European companies or those scaling volume affordably; strong transactional email usage alongside marketing
- Beehiiv or Substack — newsletter-first business, audience monetization is a core part of the strategy
- HubSpot email — part of a broader HubSpot investment; marketing and CRM are unified, usually B2B
- Customer.io or Iterable — product-led growth company, heavily automated lifecycle email triggered by user behavior, almost certainly a SaaS product with real engineering investment in email
These patterns aren't universal, but they're directionally useful — especially when combined with other signals from their tech stack. A Klaviyo + Shopify + ReCharge combination tells you they're running a subscription e-commerce business with a serious retention operation. A ConvertKit + Webflow + Stripe combination suggests a solo creator selling digital products or courses.
Bottom Line
Figuring out what email marketing software a company uses takes under a minute using any of the methods above. Check their subscribe forms and pop-up scripts for platform-specific embed domains. Look at their DNS SPF record to see which sending infrastructure they've authorized. If you've received their email, the unsubscribe link and headers tell you directly. For the fastest workflow across all of these, SaaS Detective automates the browser-side detection — it catches Klaviyo, Mailchimp, ActiveCampaign, ConvertKit, Drip, Brevo, GetResponse, and more in one click on any page you visit.