Checkout Form Optimization: What Glued Fixes and Why It Moves Conversion

Checkout form optimization is the process of removing unnecessary fields, fixing input types, and improving validation so customers complete purchases instead of abandoning them. Glued's data across 350+ DTC projects shows most stores have the same five fixable problems, and the highest-impact ones take less than a day to implement.

Baymard Institute's 2025 research identifies form-related issues as the third-leading cause of checkout abandonment, behind unexpected shipping costs and forced account creation. The majority of form friction falls into two categories: fields that don't need to exist, and mobile input experiences that weren't designed for how customers actually use their phones.

This is a tactical guide. Each section covers a specific problem, how to identify it in your store, and the implementation detail to fix it.

The Required vs. Optional Audit

Most DTC checkout forms collect more information than they need. The test: for each field, ask whether the order can be fulfilled without it.

Required for fulfillment:

• Email address (order confirmation, shipping updates, customer service contact)
• Shipping address: recipient name, street address, city, state/province, postal code, country
• Payment information: card number, expiration, security code, billing name

Almost never required for standard DTC fulfillment:

• Phone number. Most carriers use email for delivery notifications. Most brands don't actually call customers. Making phone optional, or removing it, reduces form length without affecting operations.
• Company name. B2C orders don't need it. Creates visual clutter and implicit complexity for consumers who don't think of themselves as business customers.
• Address line 2. Apartment and suite numbers can be collected in address line 1 for the majority of orders. A collapsible "Add apartment, suite, or unit" option reduces visual form length without losing the field for customers who need it.
• Birth date, gender, marketing preferences. These are post-purchase data collection opportunities, not checkout requirements.

Glued's data across 350+ projects shows most DTC checkout forms have two to four fields that could be removed or made optional without affecting a single order's fulfillment. Baymard Institute's 2025 research found the average US eCommerce checkout has 11.8 form fields, nearly three times the minimum required.

The goal isn't the minimum possible, it's the minimum necessary. Don't remove fields your operations genuinely depend on. Do remove every field that exists because it seemed useful when the store was set up.

Mobile Input Type Optimization

This is the highest-ROI fix in checkout form optimization, and it's consistently overlooked because it's invisible on desktop. When a customer on an iPhone taps a postal code field and a full QWERTY keyboard appears instead of a numeric keypad, that's a friction point caused by a single missing HTML attribute.

Each input type fix is a one-line change. For Shopify stores on standard plans, most are handled natively, but custom themes or third-party checkout apps often override these defaults. Audit your mobile checkout on an actual device (not a browser responsive preview) and tap through every field to verify the correct keyboard appears.

DR-HO's (Ontario, CA) mobile checkout redesign, which included explicit keyboard type optimization alongside larger tap targets and simplified information flow, contributed to a 122% overall CVR increase (Shopify analytics, 2024). Their audience (50+, many with reduced hand dexterity) made every friction point more costly than it would be for a younger demographic. But Glued's approach, designing up for the user with the least tolerance for friction, improves conversion across all demographics.

Tap Target Sizing

Apple and Google both specify 44x44px as the minimum touch target size for interactive elements. Most checkout forms are designed at desktop first and scaled down, which produces fields and buttons that are technically on the screen but difficult to tap accurately on a phone.

The practical standard for DTC checkout forms:

• Form field minimum height: 48px (slightly above the 44px minimum, accounts for border)
• Submit button minimum height: 56px
• Minimum spacing between adjacent tappable elements: 8px
• Checkbox and radio button tap zones: expand the clickable area to the label text, not just the control

Address Autocomplete

Manual address entry is the single most friction-heavy task in mobile checkout. A user typing a full street address on a phone keyboard makes more errors, takes longer, and abandons at higher rates than a user selecting their address from a suggestion list.

Google Places Autocomplete reduces address entry to three to four keystrokes for most users: type the first few characters of the street name, select from the suggestion list, and the street, city, state, and postal code populate automatically.

Shopify's native checkout includes address autocomplete. Custom checkout implementations need it explicitly integrated. Verify it's working on your mobile checkout with an actual device test, autocomplete failures are common after theme updates or app installations that modify checkout JavaScript.

For stores with significant international traffic, verify that autocomplete works for your top non-US markets. UK addresses, Canadian postal codes, and Australian state/territory selections each have specific autocomplete behaviors that may require explicit testing.

Real-Time Inline Validation

The original approach to form validation: submit the form, server checks everything, display a list of errors at the top of the page. The problem: the customer has to scroll back through the entire form to find the fields with errors, often losing context on what they already entered.

Modern inline validation shows errors immediately, adjacent to the field that caused them, as soon as the customer leaves (blurs) that field, not after form submission.

Implementation principles:

• Validate on blur, not on keystroke. Showing "invalid email" while a customer is mid-typing "name@gmail" is disruptive. Validate when they move to the next field.
• Show errors inline, adjacent to the field. Not in a banner at the top of the form. The customer's attention is where they're currently working.
• Be specific. "Invalid card number" is better than "Payment error." "This ZIP code doesn't match the state" is better than "Invalid address."
• Confirm correct entries positively. A green checkmark or subtle color change when a field passes validation reduces anxiety and reinforces progress.
• Preserve entered data on payment failure. If a card is declined, the shipping address, email, and contact fields must persist. Clearing the entire form on a payment failure is a high-abandonment scenario.

The Promo Code Field Problem

A visible, prominent promo code field on the checkout page sends a percentage of customers who don't have a code to search for one, usually in a new tab or browser search. Some of them find a code and return. Most of them don't come back.

 The fix isn't removing the promo code field, it's deprioritizing it visually. Three options in order of implementation simplicity:

• Collapsed by default. A "Have a promo code?" link that expands the field on click. Customers with codes know to look for it; customers without codes don't see it.
• Lower visual prominence. Move it below the payment summary, use a lighter text treatment, and reduce the field size.
• Disable for paid traffic audiences. Shopify Plus checkout extensibility allows conditional field display.

EBOOST's catalog reduction (from 600+ SKUs to 72 targeted products) produced a 42% CVR increase partly by removing the decision fatigue that caused customers to leave the purchase flow to compare options (Shopify analytics, 2024). The promo code field problem is the checkout equivalent: removing a visible invitation to leave the purchase flow.

Express Checkout Placement

Apple Pay, Google Pay, and Shop Pay are form optimization tools as much as payment options. For a returning customer with saved payment information, they replace the entire checkout form with one or two taps.

Placement matters. Express checkout buttons buried below the form, or visible only after the customer has already started filling out fields, capture a fraction of their potential conversion lift. The correct placement for mobile:

• Top of checkout page, above the form. Before the customer starts typing anything.
• Cart page, above "Proceed to Checkout." For customers with high purchase intent, eliminating the checkout form entirely is the highest-conversion path.
• Minimum button size: 44px height, full-width on mobile.

Shop Pay in particular: Shopify's 2024 data shows Shop Pay converts at a meaningfully higher rate than standard checkout for returning customers, primarily because it eliminates the form entirely for users who've previously used it.

Form Audit Checklist

Before making changes, audit your current form on a mobile device:

• Tap each field, does the correct keyboard appear?
• Is phone number required? Can it be made optional?
• Is address line 2 prominent or collapsible?
• Does the promo code field appear collapsed or expanded?
• Are all tap targets at least 44px (field height + button height)?
• Does address autocomplete work on mobile?
• Are errors shown inline, adjacent to fields?
• Does entered data persist after a payment failure?
• Are Apple Pay / Google Pay / Shop Pay buttons visible above the form on mobile?
• Does the form validate on blur, not on keystroke?

Each "no" on this list is a measurable conversion leak. Use Glued's Checkout Abandonment Calculator to quantify what the current form friction is costing before prioritizing which fixes to implement first.

FAQ

What checkout form fields can I remove without affecting fulfillment? Phone number (optional for most standard DTC shipping), company name (B2C orders don't need it), address line 2 (make collapsible rather than visible by default), and any marketing preference or demographic fields. The minimum required for a standard DTC order is email, shipping address, and payment information.

What's the most impactful checkout form fix? For most Shopify stores, it's a tie between input type optimization (ensuring the correct keyboard appears for each field on mobile) and express checkout placement (Apple Pay, Google Pay, Shop Pay above the form on mobile).

How do I find where my checkout form is losing customers? Install Hotjar or a session recording tool and review recordings of mobile checkout sessions specifically. Look for: customers tapping a field multiple times (wrong tap target size), customers switching away from the checkout tab (likely searching for a promo code), and customers abandoning immediately after a validation error appears.

Should I use inline validation or submit-based validation? Inline validation, showing errors adjacent to the relevant field when the customer leaves it, before form submission, consistently outperforms submit-based validation. Validate on blur (when the customer moves to the next field), not on keystroke.

What's the correct tap target size for checkout form fields? Minimum 44x44px per Apple and Google's HIG and Material Design guidelines. In practice, set form field height to 48px and button height to 56px.

How does the promo code field hurt conversion? A prominent promo code field prompts customers who don't have a code to search for one, usually leaving the checkout to do so. Most don't return. Making the field collapsed by default keeps it accessible for customers with codes without advertising to everyone that a discount might be available.