Getting maximum carrier coverage across Shippo, EasyPost, and ShipEngine

One question that comes up over and over: do I really need more than one shipping provider? Isn't Shippo / EasyPost / ShipEngine basically the same set of carriers?

The short answer: the big carriers (USPS, UPS, FedEx, DHL) are available through all three, so if you only ship with those, pick one provider and you're done. The longer answer is that regional and specialty carrier coverage diverges, and for high-volume shippers that last 10-20% of delivery options is where real money lives.

Where the three providers agree

USPS, UPS, FedEx, and DHL Express are available through all three. If you connect your carrier account to Shippo, EasyPost, or ShipEngine, you'll get the same published rates from each (carriers negotiate with you, not with the provider).

For most small-to-mid-volume shippers, this overlap is enough. You pick one provider based on developer experience or dashboard quality, and ignore the others.

Where they diverge

Regional carriers are where the real fragmentation shows up. Coverage as of early 2026:

• OnTrac (west coast, B2C): available through EasyPost and ShipEngine, limited through Shippo.
• LSO (Texas regional): available through EasyPost and Shippo, not always through ShipEngine.
• Spee-Dee (upper midwest): available through Shippo; EasyPost and ShipEngine have had it on and off.
• DHL eCommerce (low-cost bulk): all three, but service-level coverage varies.
• Axlehire, Veho, GLS: spotty availability across all three, frequently updated.

Specialty offerings (reg-freight, international consolidators, same-day couriers) are even more fragmented. If your business depends on one of these, audit the specific provider first, not the general feature set.

Why coverage matters more than it seems

For a typical e-commerce flow, a 10% shipping cost reduction translates directly to margin. Regional carriers often price 15-30% below USPS Ground for local deliveries. If your single-provider integration doesn't surface OnTrac for west-coast residential, you're leaving that savings on the table.

This isn't theoretical. Teams we've talked to who connect multiple providers see 5-15% average cost reduction on delivery spend, just from better carrier matching per-destination.

The fan-out approach

Once you decide to use multiple providers, the implementation question is: how do you query them without blowing up your rate latency?

The answer is parallel fan-out. Query all three providers simultaneously, merge the results, sort by price. Total latency is bounded by the slowest single provider, not the sum of all three.

// The naive approach: sequential, ~6 seconds for three 2-second calls
const shippoRates = await fetchShippo(request);
const easypostRates = await fetchEasyPost(request);
const shipengineRates = await fetchShipEngine(request);

// Parallel: ~2 seconds total (max of the three)
const [shippoRates, easypostRates, shipengineRates] = await Promise.all([
  fetchShippo(request),
  fetchEasyPost(request),
  fetchShipEngine(request),
]);

// Even better: Promise.allSettled so one slow/failing provider
// doesn't kill the others
const results = await Promise.allSettled([
  fetchShippo(request),
  fetchEasyPost(request),
  fetchShipEngine(request),
]);

Promise.allSettled is the important bit. If you use Promise.all and any provider fails, the whole thing rejects. With allSettled, you get partial results: whatever succeeded plus a list of who failed.

What to do with the merged list

Once you have rates from all three providers, you usually want to do one of two things:

• Show the cheapest N to the customer. Sort by price, take the top 3-5. The customer picks. Dedupe if two providers offer the same carrier/service (they will).
• Auto-pick the cheapest that meets your criteria. Sort, filter by estimated days, pick the first. This is the pattern for high-volume shippers who optimize by algorithm, not by customer choice.

Either way, you want normalization first. You don't want to compare rate.amount (decimal string) with rate.shipping_amount.amount (number) in the same sort. Normalize once at the adapter boundary, then work with a single shape.

The short version

If you're shipping USPS-only, one provider is fine. If you're shipping at volume, connect multiple. The cost of doing so (one extra API account) is dwarfed by the benefit (better per-shipment rate matching).

Our SDK handles the fan-out, normalization, partial-failure handling, and sorted result merging out of the box. One client, three providers, one typed response. Zero runtime dependencies. Install with npm install rateship.