Sharing a cart between subdomain and main storefront (configurator use case)

[jwhscholten]

I’m building a custom product configurator that needs to live on a subdomain (e.g. config.example.com). After configuring a product, the user should be able to continue shopping and check out on the main storefront (www.example.com) with the configured items already in their cart.

I’m trying to understand the intended / supported way to do this in Swell.

Specifically:

1. Cart + cookies

   • Are Swell cart/session cookies host-only, or can they be shared across subdomains (e.g. Domain=.example.com)?
   • If this is configurable, where should this be done?

2. Cross-domain cart handoff

   • Is there an official or recommended pattern to transfer a cart from one domain/subdomain to another?
   • For example: creating a cart via API and restoring it on the main domain using a cart ID, token, or session reference.

3. Best practice

   • For this use case, is the recommended approach:
     • a) sharing cookies across subdomains
     • b) rebuilding the cart on the main domain (passing line items/options)
     • c) proxying the configurator under the main domain
     • or something else?

I’m happy to implement a token-based redirect or cart rebuild flow if that’s the intended solution — just want to align with Swell’s best practices.

Thanks in advance!

[ericingram]

Sounds cool!

Are Swell cart/session cookies host-only, or can they be shared across subdomains (e.g. Domain=.example.com)?
If this is configurable, where should this be done?

If you're using Swell.js (the Frontend API), then it creates a cookie on whichever domain initiated the session. I suppose you could transfer the cookie to another domain manually, or use a different solution for session management.

The session basically just contains the cart_id and operates on all the same backend APIs you could orchestrate yourself as well.

Is there an official or recommended pattern to transfer a cart from one domain/subdomain to another?
For example: creating a cart via API and restoring it on the main domain using a cart ID, token, or session reference.

Going by memory here, you may be able to implement logic to create a 2nd cookie on the TLD that is agnostic to the subdomain. Whenever the configurator creates a session with a cookie for config.example.com, you could copy the value of that cookie to another one with .example.com as the domain, which should then become accessible on the main site.

I'm not sure if we have a best practice here since it hasn't come up as a common use case, but whichever solution you choose may influence our future recommendations :)

[jwhscholten]

Thanks for the detailed explanation — that clarifies things well.

So to confirm our understanding:

• Swell.js sessions are domain-scoped by default and not shared across subdomains automatically.
• The session cookie mainly contains the cart_id, and all cart operations can be orchestrated via the backend APIs.
• There’s no built-in or officially recommended cross-domain cart transfer pattern at this point.

Given that, we’ll proceed with a custom approach on our side:

• Treat the configurator as a separate app that either passes line items or a cart reference via a short-lived token.
• On the main domain, merge or rebuild the cart using the existing Swell APIs rather than relying on cross-subdomain cookie copying.

We may experiment with a TLD-level cookie, but agree that an explicit cart handoff/merge is the more robust solution.

Appreciate the insight — happy to share feedback once we’ve implemented this.

[ericingram]

Exactly right. We'd welcome suggestions to make this easier based on your experience 🙌