Shipping & Fulfillment

Multi-carrier shipping APIs

• ★ EasyPost — clean API, broad carrier support (USPS, UPS, FedEx, DHL, Canada Post, Royal Mail, etc.). Free tier with credits for testing.
• ★ Shippo — competitor; great DX; pay-as-you-go, no free tier.
• Stallion Express — Canada-focused.
• Sendcloud — Europe-focused.
• ShipEngine — owned by Auctane (ShipStation parent).
• EasyShip — global.
• Pirate Ship — discounted USPS, no API but very cheap for hobbyist sellers.

Tracking aggregators

• ★ AfterShip — best-in-class tracking + branded tracking pages + email/SMS notifications. Generous free tier.
• 17track — free tracking lookup; large carrier coverage.
• TrackingMore — competitor.
• Parcel Perform — enterprise.

Order management / OMS / multi-channel

• Shopify Flow / Shopify Fulfillment Network — bundled with Shopify.
• ShipStation — multi-channel; popular for ecommerce SMBs.
• ShipBob — 3PL with API; outsource fulfillment entirely.
• Veeqo (Amazon-owned) — free-tier OMS for multi-channel.
• Linnworks, Cin7 — paid OMSs.
• Stord — modern 3PL.

Returns

• ★ AfterShip Returns — paired with AfterShip tracking.
• Loop Returns — Shopify-focused; great UX; paid.
• Returnly (Affirm) — alternative; paid.
• Narvar — enterprise.

Rate calculation / shopping carts

• ★ EasyPost / Shippo rate API — quote multiple carriers per shipment; pick the best.
• Shopify Carrier Service API — for showing real-time rates in checkout.
• Stripe Tax + Stripe Shipping rates — built into Stripe Checkout.

Label printing

• EasyPost / Shippo generate PDF/PNG/ZPL labels.
• DYMO Connect, Zebra Browser Print — for in-browser label printers.
• Brother b-PAC — Brother's SDK.
• react-thermal-printer — open-source helper.

International / customs

• EasyPost / Shippo include customs forms generation.
• Zonos — duty / tax estimates for cross-border.
• EasyShip — same niche.
• EU IOSS / OSS schemes — talk to your tax provider; see Tax & Compliance.

Delivery / last-mile (B2C immediate)

• Uber Direct / DoorDash Drive / Postmates / Onfleet APIs — same-day delivery APIs.
• GoBolt, Stuart, Delivery.com — regional alternatives.

In-store / pickup

• Doddle, Happy Returns — pickup networks.
• Shopify Local Pickup, Bopis features in most platforms.

Integration patterns

• Quote at cart → buy label at order paid → push tracking number to customer + carrier → handle webhook events for delivered / exception.
• Webhook subscriptions for tracking events; aggregators give you one webhook for many carriers.
• Async label generation — offload to a Job Queue; some carriers are slow.
• Idempotent label requests — every API has retries; use idempotency keys.

Pick this if…

• Default multi-carrier API: EasyPost or Shippo.
• Tracking + branded pages: AfterShip.
• Outsource fulfillment entirely: ShipBob or Stord (3PL with API).
• Returns specifically: Loop (Shopify) or AfterShip Returns.
• Same-day local delivery: Uber Direct.
• Budget-tier USPS only: Pirate Ship (cheap, no API).