Diagnostics — mobile signals

Mobile Landing Page Conversion: 9 Things That Break on a Phone

Your analytics says most visitors are on a phone. Your page was designed, reviewed, and signed off on a 27-inch monitor. That gap is where conversions quietly leak. Here are the nine breakages we see most — each with the symptom you'd notice and the fix you'd ship.

The core problem

You build on desktop, your buyers arrive on a phone

Open your analytics and look at the device split. For most landing pages — especially anything reached through Instagram, TikTok, paid social, or a link in a DM — the majority of sessions are mobile. Sometimes 70%, 80%, more. Then look at where the page was actually built: a developer's wide monitor, a designer's Figma frame, a founder's laptop. The page that converts the most people is being judged on the screen the fewest people use.

Mobile isn't 'desktop, but narrower.' It's a different physical object. The screen is the size of a playing card. The pointer is a thumb, not a pixel-perfect cursor. The network is cellular, not fiber. Attention is shorter and interrupted. A layout that feels crisp at 1440px can be a cramped, slow, tap-missing mess at 390px — and you'll never feel it unless you actually hold the page in your hand.

The nine breakages below are the ones our audits flag again and again. None of them are exotic. They're the predictable result of designing for one screen and shipping to another.

The 9 breakages

What breaks on a phone — and how to fix it

Each card is a real failure mode: the symptom you'd see in a session recording, and the concrete fix. Work top to bottom — the first three move the most revenue.

1. The promise gets pushed below the fold

Symptom: on desktop your headline and value prop sit proudly at the top. On a phone, a tall logo bar, an oversized hero image, or a cookie banner eats the first screen — and the visitor scrolls into a void without ever reading what you do. Fix: on a 390×844 viewport, your core headline and a one-line subhead must be visible before any scroll. Shrink the header to roughly 56px, move decorative images below the headline, and make the cookie banner a thin bottom bar, not a full-screen wall.

2. Tap targets too small

Symptom: buttons and links that are easy to click with a mouse but require careful aim with a thumb — and people miss, hit the wrong link, or give up. Fix: make every interactive element at least roughly 44×44px (Apple's Human Interface Guidelines and Google's Material guidance both publish minimums in this range) with real spacing between adjacent links. Your primary CTA should be a full-width or near-full-width button, not a text link the size of a body line.

3. No sticky CTA

Symptom: the only 'Get started' button lives in the hero. On a long mobile page the visitor reads three screens of benefits, gets convinced — and now has to scroll back up to act. Most won't. Fix: add a sticky bottom bar with your primary CTA that appears after the user scrolls past the hero. One button, the same verb as your hero CTA, always within thumb reach. This is one of the highest-leverage mobile changes you can make.

4. Forms that zoom and jump

Symptom: tapping an input zooms the whole page in (iOS Safari does this automatically when the input font-size is under 16px), the layout shifts, the keyboard covers the submit button, and the wrong keyboard appears for the field. Fix: set input font-size to 16px or larger to kill the auto-zoom. Use the right input types (type=email, type=tel, inputmode=numeric) so the correct keyboard opens. Keep the submit button reachable above the fold of the keyboard, and cut every field you don't strictly need.

5. Slow LCP on cellular

Symptom: on your fast office Wi-Fi the page is instant. On a phone with two bars on the train, the hero image takes several seconds to paint and the visitor is gone before the headline lands. Fix: compress and properly size the hero image (serve a smaller asset to mobile), lazy-load everything below the fold, defer non-critical scripts, and preload the one image that is your Largest Contentful Paint. Test on a throttled 'Slow 4G' profile, not your desk connection.

6. Contrast and text too small to read

Symptom: light-grey body text on white, 12px copy, thin display fonts — legible on a calibrated monitor, unreadable on a phone outdoors in sunlight. Fix: body text 16px minimum, a contrast ratio of at least 4.5:1 for normal text (the WCAG AA threshold), and no critical copy in light grey. If you have to squint while holding your phone at arm's length in daylight, your buyer won't bother.

7. Desktop popups on mobile

Symptom: a centered email-capture modal or exit-intent popup designed for desktop appears on mobile, covers the whole screen, and its close button is a tiny X in a corner the thumb can't comfortably reach. The visitor's only escape is to leave the page entirely. Fix: either suppress intrusive interstitials on mobile or replace them with a dismissible bottom slide-up that has a large, obvious close control. Google has publicly stated it down-ranks intrusive mobile interstitials in search, so this is a ranking issue too.

8. Horizontal scroll

Symptom: the page can be swiped sideways, content runs off the right edge, and a fixed-width element (a wide table, an un-wrapped code block, an image with a hardcoded pixel width) breaks the layout. Nothing screams 'not built for phones' louder. Fix: ensure a single, vertical scroll axis. Set max-width:100% on media, let containers be fluid, and check that no element has a fixed width wider than the smallest viewport you support.

9. CTA outside the thumb zone

Symptom: the primary button sits in the top corner or dead center-top, where a thumb holding the phone one-handed can't comfortably reach. The visitor wants to act but the geometry fights them. Fix: place the most important action in the lower-middle of the screen — the natural thumb arc — and keep the sticky CTA there. The easier it is to reach, the more often it gets tapped.

Self-audit

Test your own page in five minutes

Don't take our word for it. Pull your page up on an actual phone — or your browser's device emulator throttled to Slow 4G — and run this list. Hold the phone one-handed the way a real visitor would.

First screen

Is your headline + subhead readable before any scroll on a 390px-wide screen?
Does a cookie banner, logo bar, or hero image steal the first screen?
Can you read every line of body copy at arm's length in daylight?

Interaction

Can your thumb hit every button without aiming twice?
Is there a sticky CTA that follows you down the page?
Does tapping a form field zoom the page or hide the submit button?
Do popups cover the screen with a hard-to-reach close button?

Performance & layout

Does the hero image paint fast on a throttled connection?
Can the page be scrolled sideways at all? (It shouldn't.)
Is the primary action inside the natural thumb arc, low-center?

Where this fits

Mobile is one signal, not the whole diagnosis

Mobile breakages are the kind of problem that hides in plain sight because the person who can fix it never experiences it. But a phone-friendly page is necessary, not sufficient. If your offer is vague, your CTA is weak, or your page makes a claim the visitor doesn't believe, fixing tap targets won't save it. Mobile signals are one dimension in a larger picture.

That's why we treat mobile_signals as one of twelve dimensions in our scoring rubric rather than a standalone checklist. Clarity, value proposition, CTA, trust, social proof, objections, form friction, offer specificity, urgency, proof, and page-speed signals all interact — and a weak score on any of them caps the others.

Mobile fixes land best on a page that's already saying the right thing to the right person, so it pays to check the whole picture in order.

A full landing page audit walks every one of those dimensions in order, so a mobile fix lands on top of a page that's already saying the right thing to the right person.

The rubric

How we score mobile signals

When we evaluate mobile_signals, we're not eyeballing 'does it look okay on a phone.' We check concrete things: does the promise survive the fold at a real mobile width, are tap targets sized for a thumb, is there a persistent way to act, do forms behave, does the hero paint fast on a constrained network, and is anything forcing horizontal scroll. Each gets a verdict and a fix, not a vibe.

If you want to see exactly how this dimension — and the other eleven — are defined and weighted, the methodology page lays out the full rubric and what a passing vs. failing score looks like for each one.

Run it now

See what breaks on your own page

You can spend an afternoon checking these nine things by hand — and you should at least pull your page up on a phone before you do anything else. But if you want a faster read, our tool checks mobile signals automatically as part of a wider conversion diagnosis.

Paste your URL into the free mini-audit and you'll get your top three fixes in about 60 seconds — including whether your promise survives the mobile fold, whether your CTA is reachable, and where your page leaks on a phone. No fluff, no GPT-wrapper guesswork, just the specific things to fix first.

Paste your URL and run the free audit — it checks your mobile signals along with the rest of the twelve dimensions, and tells you exactly where to start.

Frequently asked

Questions, answered

Why does my landing page convert worse on mobile than desktop?

Usually because the page was designed and reviewed on a large screen and never properly tested on a phone. The most common culprits are the headline getting pushed below the fold on a small viewport, tap targets that are too small for a thumb, no sticky CTA so people have to scroll back up to act, forms that zoom or hide the submit button, and a hero image that loads slowly on cellular. Each one is fixable; you just have to experience the page the way a phone visitor does.

What is the minimum tap target size for mobile buttons?

Both Apple and Google publish minimums in the range of roughly 44×44px (Apple's Human Interface Guidelines and Google's Material guidance both land near this size). For a primary CTA, go bigger — a full-width or near-full-width button with clear spacing around it. The goal is that a thumb can hit it on the first try without zooming or aiming carefully.

How do I stop iOS from zooming in when someone taps a form field?

Set the font-size of your input fields to 16px or larger. iOS Safari auto-zooms whenever you focus an input with text smaller than 16px, which causes the jarring zoom-and-jump effect. While you're at it, use the correct input types (type=email, type=tel, inputmode=numeric) so the right keyboard appears for each field.

Should I show the same popups on mobile as on desktop?

No. A centered desktop modal becomes a full-screen wall on a phone with a close button that's hard to reach with a thumb, which often forces visitors to leave the page entirely. Either suppress intrusive interstitials on mobile or replace them with a dismissible bottom slide-up that has a large, obvious close control. Google has also said it down-ranks intrusive mobile interstitials, so it's a search issue as well as a UX one.

Why does my page load fast for me but slow for visitors?

Because you're almost certainly testing on fast Wi-Fi on a powerful device. Real mobile visitors are often on a throttled cellular connection on mid-range phones. Test using your browser's device emulator set to a 'Slow 4G' profile, then compress and size your hero image appropriately, lazy-load below-the-fold content, defer non-critical scripts, and preload the single image that is your Largest Contentful Paint.

How can I quickly check if my landing page is mobile-friendly?

Pull the page up on an actual phone, held one-handed, the way a real visitor would. Check whether your headline is readable before scrolling, whether your thumb can hit every button, whether there's a sticky CTA, whether forms behave, and whether the page can be scrolled sideways at all. For a faster, scored read, paste your URL into a free mini-audit — it flags the specific mobile breakages along with the rest of the conversion picture.

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