How We A/B Test Hero Sections With One Script Tag (And What 128K Impressions Taught Us)

#showdev #webdev #startup #javascript

The Problem

Every time you ship a new hero section, you're making a bet. You're betting that this headline, this layout, this CTA will resonate with your visitors.

But most teams never actually verify that bet. The design ships, traffic flows through it, and nobody checks if a different version would have performed better.

That's the exact problem we built Lemora to solve.

What Is Lemora?

Lemora is an A/B testing tool built specifically for hero sections. It runs controlled split tests and surfaces AI-analyzed insights on which layout, copy, and imagery actually converts — without requiring you to build custom experiment infrastructure.

The core idea: one script tag in your <head>, and your hero section starts running A/B tests automatically.

How It Works Under The Hood

When you set up a test in Lemora:

You register your domain and get a unique embed script URL
You paste your hero section HTML/CSS variants directly (full creative control, no limitations)
You configure traffic weights (e.g., 50/50 or 70/30 gradual rollout)
You add one <script> tag to your site's <head>

The script handles:

Weighted random variant selection per visitor
CSP-safe DOM injection (works with Shopify, WordPress, any CMS)
Impression and click tracking via CORS-compliant requests
Session persistence so visitors always see the same variant

Here's the full integration code:

<!-- Add this to your <head> -->
<script src="https://lemora.cloud/api/embed.js" async></script>

That's genuinely it. No SDK setup, no component wrappers, no build tool configuration.

What 128,904 Impressions Taught Us

We've been running live tests across multiple sites. Here's a real snapshot from one of our active experiments:

Variant	Type	CTR
A	Original	8.4%
B	Social proof	11.7%
C	Focused CTA	9.9%

Best uplift: +18.3% (Variant B vs baseline)

The social proof variant significantly outperformed the original. This is a pattern we keep seeing across tests — developers and marketers tend to over-invest in headline copy and under-invest in proof elements like customer logos, testimonials, and usage numbers.

Key Technical Decisions

Why DOM injection instead of server-side rendering?

DOM injection via a script tag means zero server infrastructure changes for the customer. Works with static sites, CMSes, Shopify themes, everything. The tradeoff is a brief flash-of-original-content for some users, which we mitigate by running the script early and making it async.

Why not use an existing tool like VWO or Optimizely?

Those tools are built for full-page testing with complex visual editors. They're heavy, expensive, and overkill when you just want to test your hero. Lemora is purpose-built — lightweight, fast, and focused on one thing.

AI-powered insights:

Instead of just showing you raw CTR numbers, Lemora runs AI analysis on variant performance and surfaces actionable recommendations (e.g., "Variant B's social proof block is the likely driver of uplift — consider testing more specific customer names vs. logos").