FeeLayer vs. Upcharge
Both are Shopify credit card surcharge apps. They take very different architectural approaches, and that drives most of the differences merchants care about. Here's how they actually compare.
- JavaScript injection-based fee logic
- No Cart Transform Functions
- No second enforcement layer
- Tiered pricing, entry plan starts at $9.99/mo
- Bypassed by Shop Pay express checkout in many configurations
- Cart Transform + Checkout Validation Functions
- Server-side enforcement, runs in Shopify’s infrastructure
- Two enforcement layers (recalc + tamper rejection)
- Flat $9/mo, no tiers, no volume caps
- Bypass-proof on Shop Pay, Apple Pay, and Google Pay
Everything the leaders offer, at 20% of the price
Compared against the top surcharge apps on the Shopify App Store. Feature checks are based on publicly documented behavior and pricing as of April 2026.
Cart Transform Functions
Checkout Validation Functions (2nd enforcement layer)
Bypass-proof on Shop Pay, Apple Pay, Google Pay
US state compliance auto-waive
Card-brand caps enforced (Visa 3% / MC 4%)
POS + online parity
Theme App Extension (storefront disclosure)
Abandoned-cart safe (no draft orders)
Pricing model
Monthly price (entry plan)
Source: Shopify App Store listings, vendor websites, and user-review analysis, April 2026. Features reflect default behavior on each app's entry-level plan; higher-tier plans may add capabilities that are only listed on paid tiers. Pricing shown is the lowest public plan, excluding free trials.
Most fee apps get bypassed at checkout.
Apps that rely on JavaScript injection or Checkout UI Extensions alone get stripped by Shop Pay, Apple Pay, and Google Pay. FeeLayer runs inside Shopify's infrastructure as two WebAssembly functions, so fees are enforced server-side.
JS injection + UI extensions
What most Shopify surcharge apps are running today.
- Express checkout (Shop Pay, Apple Pay, Google Pay) skips the UI extension
- Customers can strip the line-item fee from cart
- Cart Transform collisions when bundles are installed
- Mobile browser inconsistency (Android / iOS Safari)
Cart Transform + Validation Functions
Shopify's newest architecture, adopted here, not retrofitted.
- Server-side recalc on every cart mutation
- Checkout Validation rejects orders with tampered totals
- Express-checkout safe. Functions run before payment auth
- Theme App Extension for storefront disclosure
What to actually evaluate
Whichever surcharge app you're considering, run these questions against each option:
- Does the fee survive express checkout? Shop Pay, Apple Pay, and Google Pay all skip most legacy injection paths. The app needs server-side enforcement (Cart Transform Functions) for the fee to apply consistently.
- Is there a second enforcement layer? Without Checkout Validation Functions, a motivated customer can theoretically modify totals before payment auth. FeeLayer\u2019s second layer rejects orders where totals don\u2019t match.
- Does it handle US state compliance? Surcharging is prohibited in Connecticut, Massachusetts, and Maine. Card-brand caps apply (Visa 3%, Mastercard 4%). Debit is prohibited under Durbin.
- Pricing model. Tiered apps punish growth, the more you grow, the more you pay. Flat-rate apps charge the same at $1K/mo as at $1M/mo. FeeLayer is flat, Upcharge is tiered.
- POS + online parity. If you have a physical store, the same fee rules need to apply at the register. Mismatched online/offline rules confuse customers and staff.
Try FeeLayer free for 14 days
Install from the Shopify App Store. No credit card required to start.
One app. Three modules.
Recover every dollar lost to processing fees. Stack all three for flat pricing with no volume caps.