Can I run a preorder only in certain markets or countries? (Essent Preorder Back in Stock app)

Yes, on the Starter plan or higher.

Choose where the preorder runs

Campaign → Content → Markets → Specific markets → add the markets → Save and Publish. Shoppers in other markets see the normal Add to cart, or your Sold out text.

Choose which stock counts

Preorder → Settings → General settings → Markets & locations → Manage. For each market, tick the locations whose stock should decide when preorder turns on. Only locations that fulfil online orders count.

Good to know

• Shopify's "Continue selling when out of stock" is one setting per variant, not per market.
• The app can't pick which location ships a preorder. Shopify's order routing decides that.
• Back in Stock alerts follow the same Markets & locations map, so a Canadian restock only emails Canadian subscribers.

Full guide: Market & location settings.