Shopify Scripts stopped executing on 30 June 2026, so any remaining Script-dependent discount, shipping or payment logic must be replaced. The migration is not a code conversion: each Script must be mapped to the appropriate Shopify Function API or supported app, rebuilt, tested against real cart scenarios and monitored after rollout.

Why this decision matters

The visible product or tactic is only one part of the operating system. The real decision includes people, workflow, data, integrations, governance, failure recovery and measurement. A technically possible route can still be commercially weak if it creates manual reconciliation, review burden, unclear ownership or a poor customer experience.

Start by naming the accountable business owner and the outcome the organisation expects. Record the present baseline and the conditions under which the decision will be revisited. This prevents feature enthusiasm from becoming an unmeasured long-term dependency.

The wrong way to evaluate it

Do not begin with a pricing table, demo or isolated traffic metric. Vendor pages describe capabilities, not the organisation’s implementation. Do not compare options using different data, easier scenarios or unequal expert support. Do not assume more automation, messages, events or features automatically create more value.

The evaluation should expose difficult states: invalid input, incomplete data, refunds, failures, permissions, multiple markets, review exceptions and handoff to another team. The deciding constraint usually appears outside the happy path.

Decision scorecard

Score business fit, user workflow, data and integration, security and privacy, performance, governance, support, portability, commercial model and internal ownership. Weight the criteria. A mandatory regulatory, checkout or data requirement should not be averaged away by several minor conveniences.

Require evidence for every high-weight score. Evidence can be an official capability, controlled test, architecture review or signed operational commitment. Treat unverified assumptions as risks, not as benefits.

Implementation deep dive

Migration inventory

Export the Scripts customisations report and read each Script in the now read-only context where available. Record business owner, trigger, inputs, priority, exclusions, customer tags, markets, selling plans and expected outputs. Remove dead rules before rebuilding them.

API mapping

Map line-item logic to Discounts, Cart Transform or Cart and Checkout Validation as appropriate; shipping logic to Delivery Customisation or Discounts; and payment logic to Payment Customisation. Confirm current plan and API availability.

Architecture

Decide whether each Function belongs in a public app, custom app or existing platform app. Separate merchant configuration from execution logic, keep versioned configuration and define how non-technical teams change rules safely.

Testing

Build a scenario matrix covering currencies, markets, customer tags, subscriptions, bundles, mixed carts, thresholds, discounts, shipping methods and payment methods. Compare old expected outcomes with Function outputs.

Cutover

Deploy behind controlled conditions, validate with tagged customers, monitor errors and conversion, then widen exposure. Maintain a documented rollback or disable path and train the ecommerce operations owner.

Representative pilot

Use this production-like scenario: inventory every line-item, shipping and payment Script; map its rules, dependencies and failure behaviour; then validate the replacement with tagged test customers before broad enablement. Freeze the inputs, acceptance criteria and measurement method before testing. Record all manual interventions and expert corrections because they represent future operating cost.

Measure rule parity, checkout correctness, latency, error logs, merchant configurability and rollback readiness. Add quality and risk observations next to numerical results. A faster workflow is not a win when it causes more defects, complaints, support work or financial reconciliation.

Architecture and data

Map every system, event, identifier, data owner and transfer. Decide which platform is authoritative for each record. Document how duplicates, delayed events, retries and partial failures are resolved. Avoid storing sensitive or unnecessary data merely because the product makes collection easy.

Where APIs or webhooks are involved, use authentication, signature verification, idempotency, event replay and observable state transitions. Where content or campaigns are involved, preserve version, source, approval and attribution records.

Governance

Define administrators, editors, reviewers, service owners and escalation paths. Apply least privilege, separate production and test access, protect secrets and document material configuration. Review the exact plan, region and setup; generic provider assurances do not replace deployment-specific assessment.

Create change control for pricing, tax, policy, platform, market or model updates that could invalidate the decision. Assign a recurring review owner instead of relying on the original implementer’s memory.

Commercial model

Model one-time implementation, migration, configuration, training and QA separately from recurring subscription, processing, app, infrastructure, support and staff effort. Include the cost of errors, abandoned processes and exit. Use current official commercial terms at the decision date and the organisation’s actual usage assumptions.

Do not publish a universal cheapest option. Commercial suitability changes with order mix, customer geography, transaction pattern, team capability and support needs.

Project Supply can translate this decision into an implementation and measurement plan. Explore Digital Engineering: Project Supply service overview or discuss the project at Contact Project Supply.

90-day execution plan

Days 1–15: document requirements, baseline, owner, data boundaries and failure cases.

Days 16–30: run the representative pilot and close high-risk unknowns.

Days 31–60: implement integrations, content or code, permissions, QA, training and rollback.

Days 61–90: measure production outcomes, remove avoidable complexity and decide whether to scale.

Measurement

Build a balanced scorecard across outcome, quality, cycle time, variable cost, rework, adoption, policy exceptions and customer impact. Establish a baseline before rollout and document attribution limitations.

Review leading signals weekly during rollout and commercial outcomes after a meaningful operating window. Stop or redesign when observed results contradict the business case.

What not to do

Do not automate an unclear process, launch to every user at once, suppress negative evidence, or preserve an unsuccessful setup because migration has already consumed effort. Sunk cost is history. A professional decision remains reversible and evidence-led.

Do not let a tool define policy, customer promise or data ownership. Technology should enforce an intentional operating model, not quietly become one.

Project Supply can translate this decision into an implementation and measurement plan. Explore Digital Engineering: Project Supply service overview or discuss the project at Contact Project Supply.

Production migration controls

Inventory every Script dependency

Create a catalogue of line-item, shipping and payment Scripts, the business rule each implements, its owner, affected markets, prerequisites and fallback. Trace dependent themes, apps, checkout customisations and operational workarounds. Group rules by Function target instead of translating file by file. This exposes duplicate logic and rules that should be retired rather than rebuilt.

Design for Function constraints

Treat Functions as bounded extensions within Shopify’s platform model. Separate deterministic commerce logic from data preparation, configuration and administration. Define configuration ownership, versioning and safe defaults. Where a requirement is not supported by the relevant Function API, document the gap and choose a supported app, a redesigned promotion or an explicit operational control instead of hiding unsupported behaviour.

Build a scenario-based test matrix

Test normal carts and collisions: stacked discounts, subscriptions, bundles, gift cards, customer segments, multiple currencies, partial fulfilment, accelerated checkout and boundary values. Record the expected result for every scenario before implementation. Run legacy and replacement logic against the same fixtures where possible, then have commercial owners approve differences rather than leaving acceptance solely to developers.

Plan cutover and rollback

Release behind controlled configuration, preserve evidence of the previous rules and define a rollback that restores a safe commercial state. Coordinate merchandising, support and finance because a technically successful deployment can still create margin leakage or customer confusion. Monitor rejected operations, conversion anomalies, average discount, shipping-method availability and support contacts immediately after activation.

Govern the rule portfolio

Assign a named owner and review date to every Function. Require change notes, peer review and a commercial approval for logic that affects price, payment or delivery. Keep configuration and code in version control, limit production access and document emergency changes. Quarterly reviews should remove obsolete promotions and consolidate overlapping rules so the new architecture does not recreate Script-era complexity.

Decision workshop and acceptance gate

Representative production scenario

Use a high-volume promotion that combines customer eligibility, product exclusions, tiered discounts and restricted shipping methods. Write the starting state, expected outcome, user roles, data involved, dependencies and time boundary. Preserve failed attempts and manual interventions, because they reveal the operating effort that a polished demonstration hides. The scenario must be difficult enough to exercise the deciding constraint but small enough to repeat after configuration or implementation changes.

Cross-functional review

Include commerce, finance, merchandising, support and engineering. Ask each participant to score immediate usability, long-term ownership, risk and measurable value. Differences in scoring are evidence, not noise: they show where one team receives the benefit while another inherits administration, review or failure recovery. Resolve material disagreements in the decision memo rather than allowing them to surface after launch.

Acceptance evidence

Require cart fixtures, legacy-versus-Function outputs, discount and shipping telemetry, rollback rehearsal and commercial sign-off. Define pass, conditional pass and fail before testing. Name who adjudicates ambiguous results and prevent the team from moving the success threshold after seeing which option performs better. Keep evidence with the implementation record so future owners can understand the original assumptions and repeat the test when conditions change.

Failure and recovery

Explicitly simulate price leakage, unavailable delivery methods, rejected checkouts or rules that cannot be safely administered. For each failure, define detection, customer impact, escalation owner, containment, recovery and communication. A route is not production-ready merely because the happy path works. Recovery must be possible with the people, access and documentation available during real operating hours, not only with the original implementation specialist present.

Ninety-day governance

During the first 30 days, validate configuration and resolve high-severity defects. During days 31–60, compare real outcomes with the baseline and remove unnecessary manual work. During days 61–90, decide whether to scale, redesign or exit. Record the owner, measurement cadence, next review date and triggers that require an earlier review.

Executive decision memo

Conclude the Shopify Scripts to Functions migration work with a short decision record that states the chosen route, rejected alternatives, evidence, assumptions, unresolved risks, accountable owner, implementation boundary, success measures, review date and exit trigger. Include the source versions or access dates behind time-sensitive claims. The memo should distinguish verified facts from internal estimates and recommendations. It should also describe what would change the decision—for example, a material vendor capability change, a different customer mix, new policy requirements, unacceptable operating effort or results outside the agreed tolerance. This record prevents the organisation from repeating the same discovery and gives future teams a defensible basis for scaling, redesigning or replacing the implementation.