How to Migrate Your Custom Shopify Delivery Date Picker to Flare

Your custom delivery date picker works. It took weeks to build. It does exactly what you need — when it doesn’t break. The problem isn’t today. The problem is every Shopify platform update, every theme change, every developer invoice to fix something that stopped working after an update you didn’t request.

Since August 2024, Shopify no longer supports checkout.liquid. Every custom checkout modification must use Checkout Extensibility. If your delivery date picker was built on checkout.liquid, it’s already on borrowed time — or already broken. If it was built on Checkout Extensibility, you’re paying a developer to maintain what an app handles out of the box.

This is the migration guide for merchants who built their own delivery date picker and are ready to stop maintaining it.

The real cost of a custom delivery date picker

The build cost is the smallest part. The ongoing cost is what compounds:

Maintenance after platform updates. Shopify updates its checkout APIs, theme architecture and Checkout Extensibility framework regularly. Every update is a potential breakpoint for custom code. Your developer investigates, patches, tests and deploys. You pay for each cycle. An app handles this automatically — the vendor maintains compatibility as part of the subscription.

Checkout Extensibility compliance. Shopify requires all checkout customisations to run on Checkout Extensibility. Custom code that doesn’t comply gets flagged, throttled or removed. Flare’s checkout extension runs natively on Checkout Extensibility — 195ms average response, certified compliant, updated automatically when Shopify releases new API versions.

Developer dependency for rule changes. Your cut-off time changes from 2pm to 1pm. Your zone boundaries shift. You add a new postcode district. With custom code, every operational change requires a developer. With Flare, you change a setting in the dashboard. No code. No ticket. No wait.

Peak-traffic risk. Custom code that works at 50 orders/day might not survive Black Friday at 500 orders/day. Apps like Flare are load-tested across 700+ stores processing $10M+ in orders monthly. Your custom code is tested by one store — yours.

For a detailed cost analysis, read buy vs build for Shopify delivery date pickers →

What Flare replaces in your custom build

Every rule your custom code handles, Flare handles from a dashboard — native Checkout Extensibility block at 195ms response, postcode and ZIP code zones with unlimited zones, per-method cut-off times that update in real time, blocked dates and blackout calendars with no code to update, per-product lead times by product variant or collection, daily order caps that close dates automatically, delivery date ship date and zone tags on every order, and checkout validation that blocks invalid orders before payment.

If your custom code does something not on this list, talk to the Flare team — custom requirements are how most of Flare’s features were built.

See the full feature set →

How the migration works

Step 1: Audit your current rules. Document your zones, transit times, cut-off rules, blocked dates and product lead times. If your developer built it, ask them for the configuration — not the code.

Step 2: Configure Flare. Flare’s onboarding team matches your existing rules in the dashboard. Most configurations are complete within a day. Complex setups (multi-zone, carrier integration, capacity limits) take 2–3 days with 1:1 onboarding support.

Step 3: Test in parallel. Run Flare alongside your custom code on a staging theme. Verify the dates match. Check edge cases — cut-off boundaries, zone borders, blocked date windows.

Step 4: Switch over. Remove your custom code. Enable Flare’s checkout extension. The date picker runs natively on Checkout Extensibility — no theme code, no checkout.liquid dependency.

“The nice thing about Flare is that we don’t have to make a custom integration with our 3PL, and it is easy to set up. I spent a very long time looking for a solution in Shopify because we had this for our WordPress website. Solution found with Flare.”

— Bamboi, Netherlands · Shopify Plus

What merchants gain after migration

Zero developer dependency for rule changes. Cut-off times, zones, blocked dates, capacity limits — all changed from the dashboard. No dev tickets.

Automatic Checkout Extensibility compliance. Flare updates its checkout extension when Shopify releases new API versions. You don’t manage compatibility.

Shipping rates from the same rules. Your custom code probably handled dates only. Flare also calculates shipping rates from the same zone configuration — replacing a second app if you have one.

700+ Shopify brands trust Flare — including merchants who migrated from custom-built solutions on Shopify Plus. 99.8% order accuracy. 5.0 stars across 94 App Store reviews.

Ready to stop maintaining custom code?

Bring your zone rules, cut-off logic and delivery configuration. Flare’s team will match them — usually within a day.

Start free trial → | Book a migration call →