When you start looking at 3PLs, the first question is whether it will connect to your store. You've spent months getting orders to flow cleanly from cart to shipping label, and handing fulfillment to someone else can feel like ripping out the wiring. Integrations are not all the same. Some pull your orders on a schedule. Others react the moment a customer checks out. Some are built and maintained by the 3PL directly; others run through third-party middleware instead. A 3PL integration is the direct connection between your ecommerce store and a fulfillment warehouse's software, so orders, inventory, and tracking data move between both systems automatically. How that connection works tells you what to ask before you sign.
What a 3PL integration actually does
Strip away the jargon and an integration moves three kinds of data between your store and the warehouse.
Orders flow in. When a customer buys, the order leaves your store and lands in the 3PL's warehouse software, with the shipping address, items, and any packing notes attached.
Tracking flows out. Once the order ships, the carrier and tracking number write back to your store, so the status flips to fulfilled and your customer gets their notification without anyone typing it in.
Inventory syncs both ways. As the warehouse picks stock, your available counts adjust to reflect it.
Depth is where integrations differ. Some 3PLs pull new orders on a schedule, checking in every so often. Others get the order pushed to them the moment it's placed, a webhook firing instead of a scheduled pull. From your side, a good integration is mostly invisible. Orders stop sitting in unfulfilled status. Tracking appears on its own. Stock counts adjust as items leave the shelf.
Here's what happens when a customer places an order through an integrated 3PL:
- The order is sent from your store to the warehouse software automatically.
- The warehouse picks, packs, and labels it.
- The carrier scans it and the tracking number writes back to your store.
- Your inventory count updates to reflect what shipped.
Three questions to ask any 3PL about their integrations
A compatibility checkbox tells you a 3PL can connect to your platform. It doesn't tell you how well. Three questions separate a clean connection from one that creates work for you later.
1. Is the integration native, or does it run through middleware? In a native integration, the 3PL typically builds and maintains the connection itself. Middleware means a third-party connector sits between your store and the warehouse: an extra piece to manage, and an extra place to check when something breaks. Ask who maintains the connection, who pays for the middleware layer if there is one, and who you call when it stops.
2. What happens if the connection breaks? Connections fail. A platform changes an API, a token expires, an order hits an edge case. The question is whether you find out fast. Ask how you're notified when an order fails to sync, how quickly someone sees it, and whether there's a manual fallback so orders still ship while it's fixed.
3. How long does onboarding take once I'm ready to connect? Ask for a realistic, step-by-step timeline: connecting the integration, mapping your SKUs, moving inventory into the new warehouse, and testing a few live orders through to a shipped label. Ask what they need from you at each step, and what happens if a step slips.
How 3PL integrations work across ecommerce platforms
The mechanics shift a little depending on where you sell. Here's what to check on Shopify, WooCommerce, and Amazon.
Shopify
On Shopify, order sync is the part that matters. A native Shopify integration reads new orders straight from your store and writes tracking back once they ship, so you manage everything from the Shopify admin you already use. Watch for the difference between a real integration and a workaround. Some 3PLs connect through a generic app or a CSV export that runs on a timer. Ask how often it syncs and what happens to orders placed between runs. Integrations that subscribe to Shopify's order-creation webhook and update inventory through its Admin API react to new orders immediately, instead of checking in on a timer. Before you commit, confirm the connection is maintained by the 3PL, and ask to see how an order moves from checkout to tracking. For the platform-specific detail, see how Simpl's Shopify integration is native, with real-time inventory visibility.
WooCommerce
WooCommerce is self-hosted, which gives you control and also more variables. Your store runs on your own hosting, with your own plugins, so two WooCommerce stores can behave differently. That makes a few questions worth asking up front. Does the 3PL connect to WooCommerce directly, or through a plugin you have to keep updated? How does order sync handle your hosting setup, and what's the sync cadence? Because WooCommerce stores vary, ask the 3PL to confirm the connection works with your specific configuration before you move inventory. If it's a native connection, ask who keeps it working when WooCommerce or your plugins update; if it runs through a plugin, ask the same question, plus who you call if the plugin breaks. See how WooCommerce fulfillment connects natively instead of through a separate plugin.
Amazon Seller Central (FBM)
Plenty of brands sell on their own store and on Amazon at the same time. If you run Amazon alongside Shopify or WooCommerce, the integration question gets a second layer: how does the 3PL route orders from more than one channel, and how does it keep inventory accurate across all of them? Ask what happens when the same SKU sells on Amazon and your store within minutes of each other. Ask whether orders from every channel land in the same warehouse and whether inventory counts update as items ship. For merchants fulfilling Amazon orders themselves rather than through FBA, see Amazon FBM fulfillment for the platform-specific setup.
How Simpl's integrations work in practice
At Simpl Fulfillment, the connection is built in. You connect your store, orders route to our warehouse automatically, and tracking writes back as soon as they ship. Simpl integrates natively with Shopify, Shopify Plus, BigCommerce, WooCommerce, and Squarespace, and with marketplaces including Amazon, Walmart, eBay, Etsy, and TikTok Shop. If you sell across several of those at once, you get real-time inventory visibility, and automated rules handle order routing and shipping-method selection. Running a custom stack? There's an open API for that.
Most merchants are connected and shipping within 5 to 7 days, and there's no separate onboarding fee to set the integration up. Once you're live, orders received before 12pm CT ship the same day. Picking, packing, postage, and packaging are included in flat-rate pricing starting at $7/order. There's a $750/month account minimum billed pay-the-difference, so you're only charged the gap if a month's fulfillment fees come in under that floor. Orders go out at 99.99% accuracy, and when something is wrong, Simpl covers the cost of correcting it. Every client also gets a dedicated account manager, reachable by email with same-day responses, so when you have an integration question there's a real person who knows your account.
See how it fits into ecommerce fulfillment end to end, or get a fulfillment quote.