Shopify eBay integration that keeps one stock count

eBay has no way to tell an app the moment something sells. So whatever connects eBay to Shopify is checking on a timer, and the honest question for any of them is how long the timer is. Ours is two minutes: we read eBay’s stock and orders every two minutes, for every connected account. A Shopify sale goes the other way in a second or two, because Shopify does announce its sales and eBay accepts the update as soon as we send it.

Back to Saturday. The eBay sale lands at 2:00. We see it by 2:02 at the latest and Shopify’s count goes to zero. If Shopify sold the same unit at 2:01, that’s the two-minute window, and it’s real. What closes it is not a faster promise; nobody can be told about an eBay sale before eBay tells them. What closes it is holding one unit back on the handful of items that sell that fast, which the next section works out. On a product that sells twenty a day, the window is a fraction of one unit and a buffer of one covers it.

The reverse direction has a different limit. eBay counts requests per selling account, across everything hitting it, so we queue exports rather than fire them at once, and when eBay refuses one we wait and resend. For one sale that’s invisible. Change 5,000 prices at once and Shopify takes it in a pass while eBay takes it at eBay’s rate, so the two can sit a few minutes apart while the batch drains. Schedule bulk price changes an hour ahead of when you want them live.

We pair a product across the two shops on its SKU, so the SKU is the one field to measure before you switch anything on. A Shopify SKU longer than 50 characters is cut to its first 50 on the way to eBay rather than refused. Nothing errors. The two stop reading as the same product and the pair quietly stops sharing a count. Long SKUs are nearly always generated ones, a supplier prefix plus a season code plus a variant string, so if yours are machine-made, sort the longest first.

The fix is dull. Shorten the SKU on the Shopify side to fit in 50 and keep it identical on both. Nothing else about the two catalogues has to match: titles, photos, descriptions and categories can differ as much as you like between a Shopify product page and an eBay listing, and most sellers want them to.

One more thing about eBay listings created from Shopify products. eBay rejects a new listing for three usual reasons that Shopify never asks about: business policies (payment, returns, postage) not set up on the eBay account, missing item specifics for the category, or a category mismatch. Fix those on the eBay side and publish again. Nothing publishes itself from QuickSync until you’ve looked at it.

Marketplace Connect is Shopify’s own channel for eBay, Amazon, Walmart and Target Plus. Install it, link the eBay account, and listings, stock and orders move with Shopify in the middle. The first 50 marketplace-synced orders each month are free; after that it takes 1% of each synced order, capped at $99 a month. Shopify’s help pages have the current terms. If Shopify and eBay are the only two shops you run and you’re under 50 marketplace orders a month, start there.

It’s built as a hub. Shopify holds the catalogue and the marketplaces hang off it, which is the right shape while Shopify is your main shop. It has no view of a Square or Clover till, an Etsy shop, a WooCommerce site or a QuickBooks count, and it can’t connect a pair that leaves Shopify out, say a Clover counter and eBay.

The two prices grow differently. Ours goes by shop: Pro is $29 a month for two shops whether they take 40 orders or 4,000. Marketplace Connect starts free and then charges per order up to its ceiling. Below 50 orders a month it’s cheaper than us. Above that the lines cross somewhere that depends on your order values, not on a number either of us prints.

Search for eBay to Shopify and most of what comes back is migration software. This isn’t that. We don’t read your eBay listings and create Shopify products out of them, and switching us on won’t fill an empty Shopify store. We match products that already exist in both shops, then keep their counts together from that point.

So if you’ve run eBay for years and opened Shopify last month: get the catalogue into Shopify however suits you, a CSV export, a migration tool, or by hand for a short range, and give each product the same SKU it already carries on eBay. That’s the only preparation that changes how well this goes. From then on, orders from both shops land in one list, the stock comes off everywhere else the moment we know, and the tracking number you add goes back onto the eBay order, where the buyer and eBay’s metrics both look for it.