Integrate Fit into your store
Keep customer authorization, inventory and order truth in your ecommerce backend.
1. Connect your catalog
Obtain a merchant key, create a store and issue store-scoped backend keys. Sync products, verified charts and variants. Maintain stable external identifiers and keep availability current. Complete the Quickstart with fictional data before connecting a real store.
2. Put the quiz on the product page
Render a ‘Find my size’ entry point and report fit_viewed through your backend. When the customer starts, create a session for the product and chosen color. Save its ID in that customer’s server-side session and render the returned questions. Do not expose your Metr key to the browser.
3. Show the recommendation
Submit only advertised answers, then show the returned size, explanation and available variants. Treat unknown fit areas as unknown. Offer the size chart and a redo action. Starting over creates a new session rather than rewriting historical answers.
4. Record the customer’s choice
Complete the session as accepted, overridden or declined. Check stock before adding to cart. Store the fit_session_id with the cart/order line so your order backend can report later outcomes. Fit does not process carts, payments or shipping.
5. Report outcomes
Send confirmed purchases and subsequent returns/exchanges/kept signals from trusted backend events. Validate ecommerce-platform webhook signatures in your adapter and reuse stable delivery IDs. Unassisted orders can omit session_id. Do not build attribution from a customer name or an email address.
6. Handle outages and retention
Use timeouts, bounded retries and the merchant’s size chart as fallback. A sizing outage must not block checkout. Agree consent and retention with the merchant. V1 provides an explicit pruning script for body answers and pseudonymous references; backups and exports need the same approved policy.
What is not included
The optional seller console supports account signup/login, store creation, scoped keys and Shopify OAuth authorization. It is not a complete Shopify app: automatic catalog sync, the storefront widget, token refresh and outcome webhooks remain pending. No JavaScript SDK, payment flow or Discover API ships with Fit V1.