Linnworks API Integrations

Linnworks sits in the middle of a multichannel operation. It holds the orders, the stock and the listings. The problem most retailers have is not Linnworks itself, it is the systems either side of it: the marketplace that needs a listing updated, the courier that needs a label, the accounting package that needs an invoice, the 3PL that needs a despatch instruction.

An integration removes the manual step between them. A customer buys on Amazon, Linnworks records the order and adjusts stock across every channel, the courier booking is raised and the tracking number sent back, and the invoice reaches your accounting system without anyone opening a spreadsheet.

The measurable outcomes are usually fewer oversells, faster despatch, and a finance month end that takes hours instead of days.

This is the part most comparison articles leave out, and it is what determines the shape and cost of a project.

Linnworks uses an application based model. You register an application in the Linnworks developer portal at developer.linnworks.com and receive an application ID and an application secret. When a Linnworks user installs that application, they receive an installation token.

Your integration then exchanges the application ID, application secret and installation token for a session token through the AuthorizeByApplication endpoint. The response includes a locality value, which tells you which regional endpoint to call, in the form https://{locality}-ext.linnworks.net/api. That session token is what authorises subsequent API calls.

Two practical consequences follow. First, an integration acts on behalf of a Linnworks user without ever storing their credentials, which is the right security posture and one reason we build this way rather than scraping or automating the interface. Second, applications can be kept private to your business or published to the Linnworks Application Store, and that decision changes the build. It is worth making deliberately at the start rather than discovering it later.

Linnworks groups its integration paths into categories that map closely onto the projects we are asked to deliver:

• Orders and despatch, including pulling orders in and pushing despatch confirmations back out
• Inventory and price updates, keeping stock and pricing aligned across channels
• Shipping integrations for courier booking, label generation and tracking
• Products and listings, creating and maintaining listings on sales channels
• 3PL and WMS integrations for businesses using external fulfilment
• Accounting integrations for invoicing and reconciliation

Most real projects touch two or three of these rather than one. A retailer moving to a 3PL, for example, usually needs despatch, shipping and inventory work at the same time.

Linnworks has a large library of prebuilt channel and courier integrations, and its Application Store carries third party apps. If one of those covers your requirement, use it. It will be cheaper and someone else maintains it. We will tell you when that is the case rather than quoting for work you do not need.

Custom development earns its place in specific circumstances:

• The system you need to connect has no Linnworks app, which is common with bespoke ERPs, older accounting systems and industry specific software
• Your workflow needs conditional logic that a generic connector cannot express, such as routing orders to different warehouses by SKU, weight or destination
• You sell the same stock across B2B and B2C with different pricing, allocation or fulfilment rules
• You need Linnworks data in a reporting layer or dashboard that reflects how your business actually measures itself
• An existing app covers eighty per cent of the requirement and the remaining twenty per cent is where the cost is

• Marketplaces: Amazon, eBay, OnBuy, TikTok Shop and other channels where a bespoke listing or order flow is required
• eCommerce platforms: Shopify, Shopify Plus, WooCommerce, Magento and BigCommerce, including headless builds
• Couriers: DPD, Royal Mail, UPS, FedEx, Evri and regional carriers, including label generation and tracking writeback
• 3PL and warehouses: despatch instructions, stock reconciliation and goods-in flows
• Finance: Xero, QuickBooks and Sage for invoicing, credit notes and reconciliation
• CRM: HubSpot, Salesforce and Zoho, so sales and service teams see order history
• Reporting: custom dashboards and BI pipelines into tools such as Power BI

Linnworks integration work tends to pay for itself for multichannel retailers running meaningful order volume across several channels, wholesalers running B2B and B2C from one stock pool, distributors with multi-warehouse routing, and any business where a person spends part of every day moving data between Linnworks and something else.

It is usually not worth it if you sell on one channel, use a courier with an existing Linnworks integration, and reconcile accounts once a month in under an hour. In that situation the prebuilt apps will serve you better than anything bespoke. We would rather say that on a discovery call than sell you a project you do not need.

1. Discovery. We map your channels, systems and current manual steps, and confirm what your Linnworks account and application access allow.
2. Design. We define data flows, field mapping, sync frequency and what happens when a call fails.
3. Development. We build against the Linnworks API in a test environment, using realistic order and stock data.
4. Testing. We test cancellations, partial despatches, refunds, oversell scenarios and API failures, not just a clean order.
5. Deployment. We go live in a controlled way, usually alongside the existing process for a short overlap.
6. Support. We monitor, alert on failures and adapt the integration as your channels change.

On pricing, we work three ways. Fixed price for a clearly scoped integration, which is what most projects use. Time and materials where the requirement is genuinely still moving. Retainer where the integration is business critical and needs monitoring and ongoing change.

On timelines, a single courier or finance connection is typically three to four weeks. A multi-system build across marketplaces, couriers and accounting is more often eight to twelve weeks. Peak trading periods are worth planning around, and we will say so if a go live date looks unwise.