How Shopify Plus Merchants Are Using Checkout UI Extensions to Increase AOV
Learn how Shopify Plus merchants use Checkout UI Extensions to increase AOV with upsells, subscription toggles, shipping bars, and smarter checkout experiences.
The short answer
Shopify acquired Checkout Blocks in January 2024 and made its Starter plan — previously $99/month — free for every Shopify Plus merchant. If you are on Plus and you need trust badges, custom fields, banners, conditional content, or basic payment and delivery method control at checkout, you no longer need to buy an app for it. Install Shopify Checkout Blocks and you are done.
You outgrow it at a predictable point: when your checkout logic needs to be conditional across many variables at once, when you need upsells inside checkout rather than only after it, and when you need to know whether any of it is actually working. Those three gaps are what the paid checkout app market now sells against, and they are the honest reason to pay for a tool like Checkout Boost, Checkout Plus, or SMART Checkout Rules.
This guide covers what free Checkout Blocks does, the four specific walls merchants hit, and which paid apps address which wall — with verified pricing as of August 2026.
What changed: Checkout Blocks became a first-party Shopify app
Checkout Blocks launched on the Shopify App Store in September 2022 as a third-party app. It became one of the most widely adopted checkout customization tools on the platform. In January 2024 Shopify acquired it.
The commercially significant part of that deal: the Starter plan, which had been priced at $99/month, became free for all merchants on Shopify Plus. It now ships as "Shopify Checkout Blocks" and is maintained by Shopify directly.
Most comparison articles written about Shopify checkout apps have not been updated to reflect this. If you read a roundup that lists Checkout Blocks as a paid third-party app at around $99/month, that article is describing a market that stopped existing more than two years ago.
What free Checkout Blocks actually covers
It is worth being generous here, because the honest answer is that it covers a lot. Shopify Checkout Blocks gives Plus merchants no-code blocks for the checkout, Thank You, and Order Status pages:
- Custom fields — gift messages, delivery notes, tax IDs, PO numbers, business details
- Custom content blocks — information banners, images, headlines, warning and success messaging
- Line item messaging and per-shipping-method dynamic content
- Hiding, renaming, and reordering payment and delivery methods
- Order value limits, enforced at checkout
- Custom discounts with conditional rules, configured beyond Shopify's default discount builder
- Display rules that determine the conditions under which a block appears
- Personalized Thank You and Order Status pages
Blocks are placed using the native checkout and accounts editor, so placement is visual rather than code-driven.
For a large share of Plus merchants, that is genuinely sufficient. If your requirement is "put a security badge above the payment section and collect a gift message," installing a paid app is a waste of money. Start with Checkout Blocks.
The four walls merchants hit
1. Conditional logic that spans multiple variables
Checkout Blocks display rules work well for single-condition logic: show this block when cart subtotal exceeds $50, or when a specific shipping method is selected. Merchants run out of room when the rule needs to combine several dimensions simultaneously — customer tag and destination market and cart contents and whether a discount is already applied and order sequence.
This is the most common reason merchants add a paid rules app on top of Checkout Blocks rather than instead of it. The two coexist without conflict.
2. Upsells inside checkout, not only after it
Checkout Blocks handles content and fields. It is not an upsell engine. Merchants who want product offers rendered in the checkout flow itself — with product selection driven by cart contents, collection membership, or recommendation logic — need a dedicated tool.
There is a real distinction here that gets blurred in most roundups. Post-purchase upsells appear on the Thank You page after payment; the customer's payment method is still authorized, so acceptance is one tap. In-checkout upsells appear before payment completes and add to the order being placed. They are different mechanics with different conversion profiles, and most apps do one materially better than the other.
3. Discount and shipping logic that Scripts used to handle
Shopify Scripts stopped executing on June 30, 2026. Plus merchants who used Ruby Scripts for tiered discounts, conditional shipping rates, or payment gating had to rebuild that logic on Shopify Functions.
Checkout Blocks covers a meaningful portion of this with its conditional discount rules. It does not cover all of it. Complex discount stacking, cart transformations, and multi-condition shipping logic generally require either a Functions-based app or custom development.
4. Measurement
This is the wall nobody markets against, and it is the one that costs the most. Checkout Blocks lets you configure a checkout. It does not tell you whether the configuration is helping.
Merchants routinely run trust badges, free-shipping progress bars, and custom fields for a year without knowing the conversion impact of any of them. Without attribution at the block level and a testing mechanism, checkout optimization is guesswork with a nice editor attached.
The paid market, with verified pricing
Pricing and positioning as listed on the Shopify App Store in August 2026. Review counts move constantly and are omitted deliberately — they measure how long an app has been distributed, not how well it solves your problem.
| App | Primary job | Pricing | Wall it addresses |
|---|---|---|---|
| Shopify Checkout Blocks | Blocks, fields, content, basic rules | Free (Plus) | Baseline — start here |
| SMART Checkout Rules & Upsells | Rule-based checkout validation and method control | Free plan; $19.99/mo for Plus | Conditional logic |
| Checkout Boost — Custom Rules | Conditions engine, in-checkout upsells, blocks | Free plan; $99/mo Pro | Conditional logic, upsells, measurement |
| Checkout Plus Customizations | Checkout and Thank You customization, upsells, free gifts | Free plan available | Conditional logic, upsells |
| Blockify Checkout Customizer | Checkout rules, customizer, discounts | Free plan available | Conditional logic, discounts |
| BeSure Checkout Rules | Checkout rules and risk controls | Free plan available | Conditional logic |
| Aftersell Post Purchase Upsell | Thank You page and post-purchase offers | Free plan available | Post-purchase upsells |
| Wiz: Checkout Upsell | Checkout and post-checkout customization | From $49/mo | Upsells |
A note on how this category writes about itself
If you search for the best Shopify checkout app, most of the results are published by companies that sell one. The pattern is consistent: a vendor publishes a "top seven apps" roundup and their own app places first. We are a vendor too, so treat this article with the same scepticism — but check the pricing claims, because that is where rigged roundups fall apart fastest. Stale or invented pricing is the tell.
Where Checkout Boost fits
Checkout Boost is a Built for Shopify certified checkout optimization app for Shopify Plus merchants. It is not the cheapest option in the table above and it is not the most widely installed. Two things make it worth evaluating.
The Conditions Engine. Checkout Boost's rule layer exposes 60+ triggers organized across 12 entity groups — cart, customer, product, order, market, delivery, payment, discount, and others — and these compose. A single block can be gated on customer tag and destination market and cart composition and existing discount state. The same engine drives content blocks, upsells, discounts, and shipping and payment method control, so the logic is written once rather than reconstructed per feature. This is the difference from a rules app that controls methods and a separate upsell app that controls offers.
The measurement loop. Checkout Boost is built around diagnose, execute, and report as one cycle rather than three tools. The Checkout Health Score identifies where a specific checkout is losing revenue, the block and rule layer implements the fix, and reporting attributes the result. Diagnosis is available on the free Starter plan; execution is gated on paid tiers.
On results: DiamondRensu recorded a 10% increase in average order value and a 3% improvement in checkout conversion rate after implementing Checkout Boost. That is one merchant, and one merchant is not a benchmark — but it is a verified figure rather than a projection.
Checkout Boost's Starter plan is free and includes the branding editor, content blocks, conditional displays, and delivery and payment option customization. The Pro plan at $99/month adds checkout upsells, post-purchase upsells, and auto add to cart. A 14-day trial covers the paid features.
Which should you choose?
A decision framework that assumes you have already installed free Checkout Blocks, because you should have:
- Checkout Blocks covers everything you need → stop. Do not buy an app. Revisit in six months.
- You need method-level rules and nothing else → SMART Checkout Rules at $19.99/month is the efficient answer. It does validation, method hiding and renaming, and shipping discount logic with a condition builder.
- Your Thank You page does nothing → Aftersell. Post-purchase is a separate surface with separate economics; a checkout app is the wrong tool for it.
- You need multi-variable conditional logic driving both content and offers, and you need attribution → this is where a consolidated tool earns its price. Checkout Boost, Checkout Plus, and Blockify all compete here; evaluate on how many conditions actually compose, and whether reporting exists.
- You are on a non-Plus plan → your options are narrower and your deadline is closer. See below.
If you are not on Shopify Plus
Checkout page customization — the Information, Shipping, and Payment steps — requires Shopify Plus. That has not changed. Non-Plus merchants on Basic, Grow, and Advanced can customize the Thank You and Order Status pages, and can use cart-stage tools.
More urgently: August 26, 2026 is the deadline for non-Plus stores to upgrade their Thank You and Order Status pages. After that date Shopify auto-upgrades the store and legacy customizations are not preserved. There is no opt-out and no grace period. Any tracking pixels, custom fields, or post-purchase logic still wired to checkout.liquid or Additional Scripts on those pages stops working.
Plus merchants already passed their equivalent deadline on August 28, 2025. If you are on Plus, this one is not yours. A number of articles currently circulating describe August 26 as affecting every store on every plan — that is incorrect.
Frequently asked questions
Is Shopify Checkout Blocks really free?
Yes, for merchants on Shopify Plus. Shopify acquired the app in January 2024 and made the Starter plan, previously $99/month, free for all Plus merchants. It is now a first-party Shopify app.
Do I still need a paid checkout app if Checkout Blocks is free?
Only if you hit one of four specific limits: multi-variable conditional logic, in-checkout upsells, complex discount or shipping logic beyond Checkout Blocks' discount rules, or block-level measurement and testing. If none of those describe you, the free app is enough.
Can I run Checkout Blocks alongside a paid checkout app?
Yes. They occupy different checkout slots and most merchants who use a paid app run it on top of Checkout Blocks rather than instead of it. Preview the full checkout on mobile after adding any app, since blocks stack differently on narrow screens.
Do checkout UI extensions require Shopify Plus?
For the checkout steps themselves — Information, Shipping, Payment — yes. Thank You and Order Status page extensions are available on non-Plus plans.
What happened to Shopify Scripts?
Shopify Scripts stopped executing on June 30, 2026. Discount, shipping, and payment logic previously written in Ruby Scripts had to be rebuilt on Shopify Functions, either through an app or custom development.
Will checkout apps slow down my checkout?
Checkout UI extensions load asynchronously and do not block the core checkout from rendering. Running many extensions simultaneously can still affect perceived performance, and visual clutter is a more common problem than latency. Add one, measure, then add the next.
How many checkout apps should I run?
Two or three well-chosen apps is a reasonable ceiling for most merchants. Each one adds UI to a page whose entire purpose is to be completed without distraction.