Sync Shopify and eBay
One source of truth for stock, so the same unit is never sold twice on two channels.
Syncing Shopify and eBay means holding one master catalogue and pushing stock changes to both channels the moment anything sells. Without it, the same unit stays listed on the second channel until someone updates it manually — which is how oversells and cancelled orders happen. SBD has run this pattern across three channels with zero mismatches.
Why the obvious approach breaks
A one-step zap will connect Shopify and eBay in an afternoon. Here is what tends to go wrong once real volume and real edge cases arrive.
Neither platform will be the master
Point-to-point sync forces you to pick a winner, and both platforms accept orders independently. The moment two sales land close together, whichever direction you chose loses one of them. A separate master catalogue is the only arrangement that holds.
Listing structures do not map cleanly
eBay item specifics, category taxonomy and variation structure do not correspond one-to-one with Shopify variants. A naive field-to-field copy produces listings that are either rejected or badly formed.
Polling is too slow for stock
Off-the-shelf connectors often poll every 15-30 minutes. For single-unit or low-stock inventory that window is exactly when you oversell. Stock decrements have to be event-driven.
eBay rate limits will bite at scale
The eBay API caps calls per day per application. A sync that updates every listing on every change hits the ceiling and starts silently failing, so updates need batching and prioritisation by what actually changed.
The actual data flows
Sale on either channel
Decrement master stock and push the new level to every other channel immediately
New product added to the master catalogue
Create the listing on both channels with channel-correct fields and taxonomy
Price or content updated centrally
Propagate to both channels, respecting per-channel pricing rules
Stock reaches zero
End or hide the listing on every channel rather than leaving it orderable
Common Use Cases
- Single-unit and low-stock inventory where oversell is unacceptable
- Launching products to multiple channels without duplicate data entry
- Channel-specific pricing from one catalogue
- Adding a third marketplace without adding manual work
Typical Stack
- Shopify Admin API
- eBay Sell API
- Airtable
- Make.com
- n8n
- Supabase
Shopify and eBay, answered
Can you add marketplaces beyond Shopify and eBay?
Yes — the master-catalogue design is what makes that cheap. We have run Shopify, eBay and Chrono24 together, and adding a fourth channel is mostly a mapping exercise rather than a rebuild, because every channel talks to the master rather than to each other.
What happens if a channel API goes down?
Changes queue rather than being lost, and replay when the API recovers. We also alert on sustained failure, because the dangerous failure mode is a sync that stops quietly while listings stay live.
Do we need to change how we list products?
You list once in the master catalogue instead of separately per channel. Channel-specific fields — eBay item specifics, for example — are held as part of the mapping, so the listing is still correct on each platform.
Related integrations
Need a different pair?
These are the integrations we are asked for most, but the approach is the same for anything with an API. Tell us what you are trying to connect and we will tell you honestly whether it needs a custom build or an off-the-shelf tool will do.
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