Illustrative previewA custom-built Shopify-to-OnBuy integration that lists your catalog,
keeps stock and prices in sync, and imports OnBuy orders back into Shopify for fulfilment. Built, installed and supported by ECOSIRE.
What is OnBuy Marketplace Connector for Shopify?
A custom-built Shopify-to-OnBuy integration that lists your catalog, keeps stock and prices in sync, and imports OnBuy orders back into Shopify for fulfilment. Built, installed and supported by ECOSIRE. Built to order by ECOSIRE for Shopify (build-to-order) — indicative price from $999.00 USD; request a quote for a scoped proposal.
Key Features
Built to order, done for you
No DIY setup — a working app, built, installed and supported by ECOSIRE.
- 1
You order
Start with a one-time build price. We scope it with you at kickoff.
- 2
We build & install
ECOSIRE builds, configures and installs it on your Shopify.
- 3
Go live + support
You go live in about one working week, with two weeks of go-live support. Defects in the code we deliver are fixed free of charge.
About this Product
OnBuy is one of the UK's fastest-growing marketplaces, and for Shopify merchants who already sell on Amazon and eBay, it's the obvious next channel to diversify into. The problem is that OnBuy has no first-party Shopify app — so most merchants either re-key listings by hand or run two stock systems that drift out of sync within days.
The OnBuy Marketplace Connector closes that gap. ECOSIRE builds, installs and supports a custom Shopify app — embedded in your Shopify admin — that treats Shopify as the single source of truth and pushes your catalog, inventory and pricing to OnBuy automatically, then pulls OnBuy orders back in for fulfilment.
This is not an instant App Store download. It is a build-to-order integration: you buy it here, we scope your catalog and OnBuy seller account, then provision and connect the app to your store. The connector authenticates to Shopify via OAuth with least-privilege scopes, reads products through the Admin GraphQL API, and listens on product, inventory and order webhooks so changes propagate in near real time instead of on a slow polling cycle.
Under the hood it maps Shopify products and variants to OnBuy listings, reconciles multi-location inventory to a single sellable quantity, handles GBP pricing and VAT-inclusive display, and applies your Buy Box and repricing rules within floors and ceilings you control. OnBuy orders are imported as native Shopify orders with line items, customer and shipping data, and tracking is written back to OnBuy on fulfilment.
You get a real channel that runs itself — with a named ECOSIRE engineer behind it, not a faceless support queue. We handle the OnBuy API quirks, the category mapping and the edge cases; you keep selling.
What you get
- A custom Shopify app, built for your store and installed in your Shopify admin (not a public App Store listing)
- OAuth connection configured between Shopify and your OnBuy seller account with scoped, revocable access
- Initial catalog mapping and a supervised first bulk-list of your products to OnBuy, with rejected listings triaged
- Configured inventory, price and order-sync rules tailored to your locations, margins and VAT setup
- UK category/attribute mapping and product-identifier (EAN/GTIN) validation set up for your catalog
- A short admin walkthrough/handover session plus written setup notes covering day-to-day operation
- Defined post-launch support window for fixes, OnBuy API changes and adjustments (scope confirmed at purchase)
Who this is for
UK multichannel seller diversifying off Amazon/eBay
Already runs Shopify plus Amazon and eBay and wants OnBuy as a lower-fee UK channel without adding a third place to manage stock by hand. Needs Shopify to stay the single source of truth so quantities never oversell across channels.
Growing Shopify brand entering the UK marketplace space
A DTC brand on Shopify ready to test marketplaces, where OnBuy's lower competition is attractive but the lack of a native connector is the blocker. Wants a done-for-you integration rather than a developer hire or a brittle spreadsheet workflow.
Operations lead at a catalog-heavy retailer
Manages hundreds or thousands of SKUs and can't risk manual listing or stock drift. Values multi-location inventory reconciliation, repricing guardrails, audit logs, and a named engineer to call when OnBuy changes its API.
How OnBuy Marketplace Connector for Shopify Compares
| Criterion | ECOSIRE | Custom Build | Competitor | Shopify Native |
|---|---|---|---|---|
| Works with OnBuy (no native Shopify app exists) | Included | Included | Partial support | Not included |
| Ready to install instantly with zero setup | Not included | Not included | Included | Not included |
| Tailored to your catalog, VAT and repricing rules | Included | Included | Partial support | Not included |
| Multi-location inventory reconciled to one OnBuy quantity | Included | Partial support | Partial support | Not included |
| Named engineer support plus OnBuy API-change maintenance | Included | Not included | Partial support | Not included |
| No in-house developer or DevOps required from you | Included | Not included | Included | Included |
| One-time price (no per-order or recurring channel fee) | Included | Partial support | Not included | Not included |
| UK category mapping with EAN/GTIN validation before listing | Included | Partial support | Partial support | Not included |
Frequently Asked Questions about OnBuy Marketplace Connector
Is this a normal Shopify App Store app I can install instantly?
No. OnBuy has no native Shopify app, so this is a build-to-order integration. After you purchase, ECOSIRE provisions a custom Shopify app for your store and installs it in your admin via OAuth. You won't find it as a one-click download, and we don't pretend otherwise — what you get is a connector configured specifically for your catalog and OnBuy seller account.
How long until it's live after I buy?
Typical delivery is around one working week from when you provide Shopify collaborator access and OnBuy seller API credentials. The exact lead time depends on catalog size and how clean your product data is (especially EAN/GTIN identifiers, which OnBuy requires). We confirm a realistic date with you at kickoff rather than quoting an unrealistic same-day install.
What ongoing support and updates are included?
Every build includes a post-launch support window (confirmed at purchase) covering bug fixes, adjustments, and updates if OnBuy changes its API or category requirements. Because this is custom software we maintain, you have a named ECOSIRE engineer rather than an anonymous queue. After the included window, ongoing support and monitoring are available as a simple maintenance arrangement.
How does inventory stay in sync if I sell on multiple channels?
Shopify is the single source of truth. The connector listens on Shopify inventory webhooks and reconciles your multi-location stock into one sellable quantity that it pushes to OnBuy in near real time. When an OnBuy order comes in, it's imported as a Shopify order so the stock decrement flows back through Shopify the same as any other sale, which is what prevents overselling across Amazon, eBay and your storefront.
Do OnBuy prices have to match my Shopify storefront prices?
No. Price sync supports channel-specific rules — you can apply a markup or margin adjustment so OnBuy prices account for marketplace fees, and you set floors and ceilings that any Buy Box repricing must stay within. All prices are handled in GBP with VAT-inclusive display appropriate to the UK marketplace.
What access do you need, and is it secure?
We connect via Shopify OAuth using least-privilege scopes — only the product, inventory, order and fulfilment permissions the connector actually needs — and you can revoke access at any time from your Shopify admin. On the OnBuy side we use your seller API credentials. We never use sql.raw-style shortcuts or store more than required, and every sync event is logged for your own audit and reconciliation.
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OnBuy Marketplace Connector
A custom-built Shopify-to-OnBuy integration that lists your catalog, keeps stock and prices in sync, and imports OnBuy orders back into Shopify for fulfilment. Built, installed and supported by ECOSIRE.
- Embedded Shopify admin app authenticated via OAuth with least-privilege scopes (read_products, read/write_inventory, read/write_orders, read_fulfillments)
- Bulk listing of your Shopify catalog to OnBuy with variant-aware mapping of products, options and SKUs
- Near real-time inventory sync driven by inventory_levels/update webhooks, reconciling multi-location stock into one OnBuy sellable quantity
- Price sync from Shopify to OnBuy, with optional channel markup or margin rules so OnBuy prices can differ from your storefront