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Conversion

Shopify Checkout Optimization

Fix the leak closest to revenue

Shopify checkout and cart optimization from the team that built CartDrawer. Checkout extensibility on Plus, cart drawer UX, express payments, mobile speed, and post-purchase offers — implemented and measured, not just recommended.

  • Checkout extensibility programs on Shopify Plus
  • Cart drawer UX — built on our own CartDrawer app
  • Express payments, mobile checkout, and speed
  • Measured tests with incremental-revenue reporting
Shopify build systemAnimated Shopify development visual with storefront modules, checkout flow, performance telemetry, and conversion architecture moving together.

Conversion architecture

About our checkout practice

We built a cart app because the cart is where stores leak

CartDrawer

Our own cart app

Checkout extensibility

Plus-native testing

Measured, not assumed

Incremental-revenue reporting

San Francisco, USA

In-house team

Conversion is a Shopify CRO and development agency headquartered in San Francisco. Running conversion programs for Shopify stores, the same pattern kept showing up: the biggest drop-off between intent and order sat in the cart and checkout, and most of the tools for fixing it were slow, bloated, or fought the theme. So we built CartDrawer — our own Shopify app for cart and checkout conversion. This service is the practice around it.

On standard Shopify, the checkout steps are fixed, so the leverage is in the cart drawer, express payment placement, shipping and trust messaging, mobile speed, and post-purchase offers. On Shopify Plus, checkout extensibility — checkout UI extensions, the Branding API, and Shopify Functions — opens the checkout itself to customization and testing. We work both surfaces, baseline everything before we touch it, and report the incremental orders each change produced.

Common checkout leaks

Where Shopify stores lose shoppers after add-to-cart

Audit enough Shopify funnels and the same leaks appear in the same places.

A slow, heavy cart between intent and checkout

Third-party cart apps and theme JavaScript that take seconds to open on mobile, fight the theme for the DOM, and hide express checkout below the fold. The shopper decided to buy and the store made them wait. A fast cart drawer with express payments visible is the single most common fix.

Surprises in checkout

Shipping cost revealed only at the last step, no free-shipping threshold messaging in the cart, unclear delivery timing, and trust content that lives on the PDP but vanishes at the moment of payment. Checkout extensibility on Plus lets us put shipping clarity and trust inside the checkout itself.

Changes nobody measured

A new cart app installed, a checkout setting toggled, an upsell added — and no baseline, no test, no idea whether completion rate went up or down. We baseline by device and source first, run changes as measured tests, and report what actually moved.

Want to know where your checkout is leaking?

Book a free 30-minute checkout audit. We'll map add-to-cart → checkout → purchase drop-off by device, benchmark it, and show you the first three changes we'd make.

30-minute call · No commitment · Custom quote in 48 hours

Shopify checkout optimization services

Every step between add-to-cart and order confirmation

Cart, checkout, payment, speed, and post-purchase — audited, engineered, and measured on Shopify and Shopify Plus.

Checkout & Cart Funnel Audit

Add-to-cart → checkout → purchase drop-off by device, traffic source, and customer type, with session recordings and speed diagnostics. Produces a prioritized fix list with projected impact before any implementation.

  • Funnel drop-off by device + source
  • Session recording review
  • Cart + checkout speed diagnostics
  • Prioritized fix backlog

Cart Drawer UX (CartDrawer)

Implementation and configuration of CartDrawer — our own Shopify cart app — or custom cart drawer UX: progress bars, shipping thresholds, upsells, express checkout placement, and a load time that doesn't make shoppers wait.

  • CartDrawer implementation
  • Free-shipping progress bars
  • In-cart upsells + bundles
  • Express checkout placement

Checkout Extensibility (Shopify Plus)

Checkout UI extensions for trust content, custom fields, delivery instructions, and in-checkout upsells; Branding API styling; and Functions for discount, shipping, and payment logic — the supported successor to checkout.liquid.

  • Checkout UI extensions
  • Branding API styling
  • Functions: discounts, shipping, payments
  • checkout.liquid migration

Express Payments & Payment UX

Shop Pay, Apple Pay, Google Pay, PayPal, and BNPL placement and testing — in the cart, on the PDP, and in checkout — so returning and mobile shoppers can finish in one tap.

  • Shop Pay + wallet placement
  • BNPL (Affirm, Klarna, Afterpay)
  • Accelerated checkout on PDP
  • Payment method ordering tests

Mobile Checkout Optimization

Mobile-first cart and checkout UX: tap targets, sticky add-to-cart and checkout buttons, address autocomplete, field reduction, and real-device speed budgets — because most Shopify checkout traffic is a phone.

  • Sticky CTA + cart access
  • Address autocomplete
  • Field + step reduction
  • Real-device speed budgets

Shopify Speed Optimization

Theme-level LCP, INP, and CLS work: render-blocking JavaScript removal, app audit and removal, image pipeline fixes, and cart-specific performance — the speed lever most checkout tools can't engineer.

  • Theme-level Core Web Vitals
  • App bloat audit + removal
  • Cart drawer performance
  • Image + font pipeline fixes

Post-Purchase Offers & AOV

One-click post-purchase upsells via post-purchase extensions, thank-you page offers, and order-status upsells — revenue captured after the risk of losing the order is gone.

  • Post-purchase extensions
  • Thank-you page offers
  • Order-status upsells
  • Offer logic via Functions

Checkout A/B Testing & Reporting

Measured tests on cart and checkout variants — checkout UI extension experiments on Plus, theme-level cart splits on standard Shopify — with incremental orders and revenue reported with confidence intervals.

  • Checkout extension experiments
  • Cart variant testing
  • Pre-registered sample sizes
  • Incremental-revenue reporting

Our checkout optimization process

Baseline, fix the floor, test the ceiling

Conversion's four-stage growth process visualized in brand blue and green
01

Audit & baseline

Funnel drop-off by device and source, session recordings, speed diagnostics, and a category benchmark. You get the prioritized fix list with projected impact — before any implementation starts.

02

Fix the floor

The non-controversial fixes ship first: express payments visible, shipping clarity in the cart, mobile speed, field reduction. These don't need tests — they need engineering. CartDrawer often lands here.

03

Test the ceiling

Measured experiments on the remaining hypotheses: checkout UI extension variants on Plus, cart drawer variants, upsell placement, payment ordering. Winners deploy permanently the week they validate.

04

Compound

Post-purchase offers, Functions-driven offer logic, and personalization layer in. Reporting shows cumulative incremental orders and revenue — the number that justifies the program.

Why Conversion for checkout

A checkout team that built the cart app

We built CartDrawer

Our own Shopify cart app, built from what we learned running CRO on Shopify stores. Cart UX isn't theoretical for us — it's a product we ship, support, and keep fast.

Checkout extensibility, natively

Checkout UI extensions, Branding API, Functions, and post-purchase extensions are the primitives we build on — the supported path on Plus, not deprecated checkout.liquid hacks.

Speed we can engineer

Theme-level Core Web Vitals work and app audits, not another 'speed app.' The cart and theme are usually the slow parts; we fix them in code.

Measured, in writing

Baselines by device and source, pre-registered tests where traffic allows, and incremental-revenue reporting with confidence intervals. You know what moved and by how much.

Standard Shopify and Plus

Cart, payments, speed, and post-purchase on every plan; checkout extensibility on Plus. We work the surface you actually have, and tell you when Plus would pay for itself.

One team from PDP to confirmation

Our Shopify CRO, development, and app teams sit together. A checkout fix that needs a Function, a theme change, and a test gets all three from one accountable team.

Frequently asked

Shopify checkout optimization questions

What is Shopify checkout optimization?
Shopify checkout optimization is the work of increasing the percentage of shoppers who complete a purchase once they've added to cart. It spans the cart (drawer or page), the checkout steps themselves, payment methods, mobile UX, speed, trust content, and post-purchase offers. On standard Shopify the checkout is largely fixed, so the leverage is in the cart, express payments, and settings; on Shopify Plus, checkout extensibility opens the checkout itself to customization and testing.
What is Shopify checkout extensibility?
Checkout extensibility is Shopify's supported framework for customizing the checkout on Shopify Plus. It replaces the deprecated checkout.liquid with checkout UI extensions (add fields, content, upsells, trust elements), the Branding API (visual styling), Shopify Functions (discount, shipping, and payment logic), and post-purchase extensions. Everything runs on Shopify's checkout infrastructure, so it stays fast, secure, and forward-compatible — and it's the mechanism behind most of our checkout experiments.
Can you optimize checkout on standard Shopify, or only Plus?
Both. On standard Shopify the checkout steps are fixed, so we focus on the cart drawer (what CartDrawer does), express payment placement (Shop Pay, Apple Pay, Google Pay, PayPal), shipping thresholds and messaging, trust content before checkout, mobile speed, and post-purchase upsells. On Shopify Plus, checkout extensibility adds the checkout itself — custom fields, in-checkout upsells, trust blocks, and Functions-driven offer logic — to the testing surface.
What is CartDrawer and how does it relate to this service?
CartDrawer is our own Shopify app for cart and checkout conversion — a fast, configurable slide-out cart with progress bars, upsells, and express checkout designed around what we learned running CRO for Shopify stores. This service is the consulting and engineering practice around it: auditing your checkout funnel, implementing CartDrawer or custom cart UX, building checkout extensibility on Plus, and testing changes so you know what actually moved completion rate.
How much does Shopify checkout optimization cost?
A checkout and cart audit typically runs $2K–$5K. Implementation ranges from a few thousand dollars for cart drawer, express payment, and settings work on standard Shopify, up to $15K–$50K for checkout extensibility programs on Plus with custom UI extensions, Functions, and an A/B testing layer. We quote fixed scopes after the audit, and offer pay-on-results structures for qualifying stores.
How do you measure whether checkout changes worked?
We baseline add-to-cart → checkout → purchase rates by device and traffic source before changing anything, then run changes as measured tests wherever traffic allows — checkout UI extension variants on Plus, cart variants via theme-level splits on standard Shopify. We report incremental completed orders and revenue with confidence intervals, not just a before-and-after screenshot.
Does checkout speed matter that much?
Yes — especially on mobile, where most Shopify checkout traffic lives. Slow cart drawers, bloated theme JavaScript, and heavy apps add seconds between add-to-cart and checkout, and every second is measurable drop-off. Shopify's hosted checkout is fast; the slow parts are usually the cart, the theme, and third-party apps loading before it. Speed optimization is part of every checkout program we run.

Related services

Checkout is one step of the whole funnel

CartDrawer

Our Shopify cart app — fast slide-out cart, progress bars, upsells, and express checkout. See the product this practice is built on.

Explore

Shopify Conversion Rate Optimization

The full-funnel program — PDP, collections, and cart testing that feeds a better checkout.

Explore

Shopify App Development

Custom checkout UI extensions and Functions when the fix needs an app, not a setting.

Explore

Shopify Plus Agency

Checkout extensibility, Functions, and the Plus features that make checkout-level testing possible.

Explore

Ready to fix the leak?

Find out what your checkout is leaving on the table

Book a free 30-minute Shopify checkout audit. We'll map the drop-off, benchmark it, and hand you the first three changes we'd make — whether or not you run them with us.

No credit card · No commitment · Pay only on results