Sign in with Google: 107% Conversion Lift (With Real A/B Test Data)

"Sign in with Google" is more than just a convenience, it's a conversion booster.

We ran a real A/B test on GenPPT and saw a 107% increase in trial starts after making Google login more prominent.

This post breaks down why it works, how you can implement it, and shares 7 real-world examples (from Reddit to Iron Company) to help you replicate the results.

• What is "Sign in with Google"?
• 7 Real-World Examples (+ metrics)
• How to Add "Sign in with Google"
• Which Google Sign-In Option Should You Use?

Updated May 2025: 107% Lift Case Study Added

What is "Sign in with Google"?

"Sign in with Google" lets users log into your website using their existing Google account—no new passwords, no forms, just a click. This secure authentication method is built on OAuth 2.0, the industry standard for delegated access.

How it works:

1. User clicks the "Sign in with Google" button on your site.
2. They're redirected to Google to review and approve access.
3. After approval, Google sends a secure token (JWT) back to your backend.
4. Your backend verifies the token and signs in (or creates) the user, providing their name, email, and (optionally) profile picture.
5. The user is instantly authenticated and ready to use your app.

Why it lifts conversion:

• Removes friction: No new passwords or forms to fill out.
• Instant onboarding: Users can sign up or log in with a single click.
• Trusted: Google's familiar UI and secure authentication build user confidence.
• Verified data: You get real, deliverable email addresses and (optionally) profile info.

Most modern web apps and SaaS products offer Google Sign-In to streamline registration and login.

Google also offers "One Tap", which overlays a simple Google account prompt directly on your site—no redirects, just a seamless, in-context sign-in experience.

Companies like Pinterest, Reddit, and Zapier have seen 20–126% conversion lifts after adding Google Sign-In or One Tap, let's take a look at some real-world examples.

7 Real-World Examples (+ metrics)

1. GenPPT: 15.5% Conversion with Google Sign-In

We ran a live A/B test on GenPPT to validate what we saw in other case studies. The results confirmed it: prominently adding Google Sign-In more than doubled our trial conversion rate.

🧪 Test Setup

We used PostHog to track conversions, React/Next.js for layout variants, and shipped updates quickly via Cursor AI. Here's what we tested:

🟥 Control: No Google Sign-In CTA

Just the standard "Start Trial" flow with no social login.

🟪 Test Variant: Google CTA in Hero + Sticky Modal

The test group saw:

• A Google Sign-In button in the hero section
• A scroll-triggered sticky modal prompting them to log in

🔍 Conversion Funnel (PostHog)

We tracked:

1. Pageview
2. Logged in
3. Landing on /app = trial start

Final conversion? From 7.48% (control) → 15.50% (test):

📈 With zero form friction and better visibility, the Google Sign-In CTA doubled conversions to trial, a +107% lift.

If you're interested in how to set this up with Next.js, React, and PostHog, we've got a full tutorial:

My Entire A/B Testing Process (FULL Tutorial with Cursor AI, React, Next, PostHog, TypeScript)

2. Promptwatch: 10.5% Conversion Rate with Google Sign-In

A prominent "Join with Google" button (in both navbar and hero) as the primary CTA—before the "Start 7-day trial"—reportedly lifted sign-up conversion to 10.5%.

Klaas

@forgebitz

·Follow

this simple CTA trick now has a 10.5% conversion rate it's an easy "trust" single for users and google signin always is extremely popular anyway

All key value props and social proof are above the fold for quick decision-making.

3. KISSmetrics: 314% Lift from Adding "Log in with Google"

• Classic A/B test: KISSmetrics ran an experiment where adding a "Log in with Google" button increased sign-up engagement from 11% to 59.7%—a 314% improvement. The test visually highlights the dramatic lift, with a clear before/after and a prominent Google login button.
• Key takeaway: Social login, especially with Google, can drive massive increases in sign-up rates when made prominent and easy to use.

4. Reddit: Nearly 2× More Sign-Ups with Google + One Tap

Reddit first launched the Google button, then layered One Tap on top—compounding the effect. The biggest gains came from mobile and desktop users who saw the overlay at the right moment.

Impact:

• +50–60% sign-ups from adding the "Sign in with Google" button (desktop & Android)
• +90% sign-ups from enabling One Tap (desktop)
• Combined: ~185% total increase in new user sign-ups

"Sign in with Google and One Tap solutions have significantly increased account creation and email coverage for Reddit by reducing friction during the account sign up flow for users. These are critical components as we continue to improve the user experience, establish long-term relationships with our users, and drive long-term retention."
—Yee Chen, Director of Product, Reddit

Source: Reddit Case Study by Google

5. Iron Company: 8× More Sign-Ups, 1.7× More Purchases

Iron Company, a long-running fitness equipment retailer, wanted to streamline account creation and boost sales. By enabling Google One Tap (via a plug-and-play extension), they made it possible for customers to sign up or sign in instantly—no forms, no passwords, just a click.

Impact:

• 8× more sign-ups after launching Google One Tap
• 70× more sign-ups via One Tap compared to their old Google button
• 25× more new accounts created with One Tap than with all other social logins combined
• 32% of all orders came from One Tap users, driving a 16% increase in total orders
• Purchase rate: Signed-in customers' purchase rate jumped from 24% to 40% (1.7× more purchases)

"Google One Tap is more than just a fast sign-in option. The return on Plumrocket Social Login Pro Extension is outstanding with almost no development effort. It helped reach key company goals providing website visitors instant access to account management and fast order placement."
—J.P. Brice, President of Iron Company

Why it worked:

• Customers could access their accounts or check out with a single click—no more abandoned carts due to long forms.
• The extension took just minutes to install and activate.
• Both mobile and desktop users benefited from the frictionless experience.

Source: Iron Company Case Study

Removing registration friction didn't just boost sign-ups—it led to more purchases and higher revenue, showing the compounding effect of seamless sign-in for e-commerce.

6. The News Minute: 8× More Sign-Ups, +15% Subscription Revenue

The News Minute (TNM), a reader-funded, women-led news publisher, wanted to make sign-up seamless and boost subscriptions. Their old flow required multiple fields and OTPs, causing drop-off and making it hard to collect emails.

By adding Google One Tap, TNM made sign-up instant—no forms, no passwords. The team implemented One Tap in about a week using a third-party service.

Impact:

• 8× more new-user sign-ups in the first 90 days
• ~9× increase in average daily sign-ups
• Nearly 100% of new sign-ups now come via One Tap
• +15% subscription revenue in 90 days after launch

"Google One Tap has helped us tremendously grow our logged-in user base and welcome them on their journey with us. For our readers, signing up on TNM has become a simple and seamless experience. The top of our funnel has increased dramatically, and is starting to have a positive impact on the number of subscriptions we are getting."
—Vignesh Vellore, CEO, The News Minute

Why it worked:

• Removed friction—no OTPs, no long forms
• Familiar, trusted Google sign-in
• More emails collected for engagement
• Larger audience for subscription offers

Source: The News Minute Case Study

Even paywalled or subscription-based media can see major uplift by making Google sign-in the default.

7. Heap Benchmark: +8.2pt Signup Lift from Google OAuth

Heap's 2025 SaaS Benchmark:
Adding a one-click OAuth option (usually Google) to the signup form increased conversion rates by +8.2% across 79 SaaS sites.

• This lift applied whether Google was shown inline or only on the dedicated sign-up page.
• Extra form fields (like company name or phone) reduced conversion.
• Companies using A/B testing tools nearly doubled their signup rates.

Source: Heap Benchmark

How to Add "Sign in with Google" (2025 Edition)

1. Make the Google Sign-In Button Obvious

   • Place the Sign in with Google button in your navbar, hero, and any sign-up modals—on both desktop and mobile.
   • For returning users or content gating, enable Google One Tap overlays for seamless access.

2. Always Offer Alternatives

   • Keep email/password and Apple ID options visible. Hiding them can reduce total conversions, even if Google's share increases.

3. Measure What Matters

   • Primary metric: completed, verified sign-ups ÷ unique visitors.
   • Secondary: activation (first key action) and retention. Social logins often boost sign-ups, but not always long-term usage.

4. Be Transparent and Secure

   • Show a clear consent notice ("We'll receive your name & email from Google…").
   • Store OAuth tokens securely. Support account deletion (GDPR/CCPA compliance).

5. Test with a Controlled Rollout

   • Run a 2-week A/B test: 50% see the new, prominent Google CTA; 50% see the old flow (or Google hidden under "More options").
   • If traffic is low, use sequential or Bayesian testing for reliable results.

For full integration steps and code, see Google's official guide.

SaaS metrics with Google Sign-In

Which Google Sign-In Option Should You Use?

• If you want maximum lift and have few compliance constraints:
  Use One Tap.
  Why: Zero-click overlay follows visitors across pages, catching them while they're still evaluating.

• If you've already redesigned your hero and need a low-code test:
  Use an inline button (in the hero and nav).
  Why: Easy to A/B; lets you piggy-back on existing CTA hierarchy.

• If you're in fintech/health-tech or need explicit consent screens:
  Use a login-page option only.
  Why: Keeps main UI unchanged; still trims friction for motivated users.

Implementation Tips

1. Show the Google button in both nav and hero for max visibility.
2. Keep an email fallback—hiding it can hurt conversions if Google is blocked.
3. Track each step: page view → button click → credential issued → onboarding.
4. Respect One Tap cooldowns—don't over-prompt or it'll disappear.
5. Share before/after sign-up charts to prove the impact.

More Resources

• Google Identity Case-Study hub – dozens more verticals (e-commerce, news, classifieds) with metrics. (Google for Developers)
• Heap's full SaaS signup benchmark – extra slices by field count, multi-step forms, etc. (Heap)
• Stytch blog roundup – tactical code snippets for injecting One Tap only after scroll/time delay. (Stytch)