How can we integrate a third party payment gateway into an ecommerce store?

Shopify Apps
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Topic summary

Goal: integrate a third‑party payment wall into a Shopify store for a hackathon proof‑of‑concept. Intended checkout flow: customer selects the new payment method at checkout and is redirected to the team’s external website to complete payment.

Current setup: a Shopify Partners account is created and a development (dev) store is available for testing.

Key questions: what is the correct integration path within Shopify—build a Shopify app, an extension, or something else—to enable a redirect‑based payment method? They want the simplest way to test the flow without creating a production app that requires approval or listing.

Constraints: this is for testing only, not a real, approved app.

Status: no answers or decisions yet; guidance on best practice and next steps is requested and the discussion remains open.

Summarized with AI on January 18. AI used: gpt-5.
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Hello, we are currently on a hackaton and we would like to integrate our payment wall into a shopify (for example)

When a potenional customer wants to check out, they select our payment method on the store, it will redirect them to our 3rd party website.

I’ve created a partners account and we have a dev store.

We are unsure what to do now, do we create an App, an extension or what is our next step?

What would be the best practice here, we just want to test it - so it wont be a real app, which must be approved etc.

Thanks a lot