May 23, 2026

Magic Link vs Password Login A/B Testing: The Case for Going Passwordless

Notion's onboarding completion jumped from 64% to 87% after dropping passwords — here's how to A/B test magic links vs password login on your site and what the data says.

Every signup form is a conversion event. And every password field is friction. In 2026, the data is overwhelming: passwordless authentication lifts conversion rates by an average of 28.3% compared to traditional password-based login. But you shouldn't take that number on faith — you should test it on your own site.

This post breaks down the real-world case studies, shows you how to set up a magic link vs password A/B test, and explains why this might be the highest-ROI experiment your SaaS team runs this quarter.

The Data: Why Passwordless Wins

The case studies are hard to argue with:

Notion saw onboarding completion jump from 64% to 87% after removing password fields entirely. Account takeover attempts dropped 89%.
Slack found that teams using magic link invitations onboarded 2.3 days faster than those requiring password setup — translating to 31% higher annual contract values.
Substack reported 41% more newsletter signups after switching to magic links.
A food delivery platform saw download-to-order conversion improve from 15% to 53% after going passwordless.

According to MojoAuth's 2026 Passwordless Conversion Impact Report, the average lift breaks down by channel: mobile conversion improves 29.6% (vs 18.4% on desktop), and ecommerce checkout conversion improves 31.4%. Cart abandonment drops 34.6%.

Speed is a big factor. Passwordless authentication completes in about 1.2 seconds on average, compared to 8.7 seconds for password-based flows. As anyone who's run page speed experiments knows, every second matters.

What to Test: Magic Links, OTP, or Passkeys?

Not all passwordless methods are equal. Magic links remain the most widely deployed method (41% of implementations) because they work universally — no app download, no biometric hardware required. But you have options:

Magic links — user enters email, clicks a link sent to their inbox. Lowest friction, but depends on email delivery speed.
Email/SMS OTP — user enters a one-time code. Slightly more friction than magic links, but doesn't require switching to email.
Passkeys — biometric or device-based authentication. Fastest completion (99% of users who start passkey signup finish it), but requires device support.
Social login — Google/GitHub/Apple sign-in. Fast, but some users distrust sharing data with third parties.

The right answer depends on your audience. Developer tools might lean toward GitHub OAuth. Consumer apps might favor passkeys. B2B SaaS often gets the best results from magic links, because business users check email constantly.

How to Run the A/B Test

If you've never run an A/B test before, the setup here is straightforward. You're testing two signup or login flows against each other:

Control (A): Your current password-based signup form (email + password + optional confirm password).
Variant (B): A magic link flow (email only — user clicks a link in their inbox to complete signup).

Key Metrics to Track

Signup completion rate — what percentage of users who land on the signup page actually finish creating an account?
Time to first action — how quickly do new users reach their "aha moment" after signup?
Return login rate — do users come back? Password reset requests drop to zero with magic links, but some users find inbox-switching annoying for repeat logins.
Support ticket volume — password resets typically account for 20-40% of support tickets.

Sample Size and Duration

Signup is a relatively low-frequency event, so you'll need enough traffic to reach statistical significance. For most SaaS sites, plan for 2-4 weeks. If you're working with limited traffic during onboarding, focus on signup completion rate as your primary metric — it has the highest event volume and will reach significance fastest.

A tool like PageDuel makes this easy to set up without engineering involvement. You can create variants of your signup page, split traffic 50/50, and track conversion events — all for free.

Watch Out for These Pitfalls

Magic links aren't universally better. Here's what can go wrong:

Email deliverability delays — if your magic link takes 30+ seconds to arrive, users bounce. Use a reliable transactional email provider and set expectations ("Check your inbox — arrives in under 10 seconds").
Corporate firewalls — some enterprise email systems strip or block magic link URLs. If you serve B2B enterprise customers, test with that segment specifically.
Repeat login friction — magic links are great for first-time signup but can frustrate power users who log in daily. Consider magic links for signup and passkeys or "remember me" sessions for return visits.
Mobile email app switching — on mobile, tapping a magic link opens the browser, but the user might be in-app. Deep linking can solve this, but it adds implementation complexity.

What the Winners Do Differently

The companies that get the biggest lifts from magic links share a few patterns:

They remove the password field entirely — not just adding a "Sign in with magic link" option alongside password. Notion's 23-point lift came from eliminating passwords, not offering an alternative.
They optimize the email — the magic link email itself is a conversion event. Subject line, CTA button copy, and expiry window all matter. A/B test these too.
They set the right session duration — long-lived sessions (30+ days) reduce how often users need to re-authenticate, which offsets the repeat-login friction.

If you're running a SaaS product, this test belongs near the top of your experimentation roadmap. The MojoAuth data suggests you should target a 25-35% conversion improvement — if your test falls below that range, check your email deliverability and mobile flow before concluding magic links don't work for your audience.

Get Started Today

You don't need to rebuild your auth system to test this. Start with your signup page: create a variant that replaces the password field with a "We'll email you a login link" flow, split traffic 50/50, and measure signup completion over 2-4 weeks.

PageDuel lets you set up this kind of experiment in minutes — no code changes, no developer bottleneck, completely free. Because if Notion can lift onboarding completion by 23 percentage points just by dropping a form field, it's worth testing on your site too.