Ship on your own USPS account
Connect the USPS developer app you already have, or create one, and your store holds the credentials securely. Your rates, your contract, postage from your own EPS account, with nobody in the middle taking a cut.
USPS APIs v3, OAuth 2.0 client credentials. The consumer key and secret are encrypted on submission and used server-side only. Calls leave from an address USPS accepts, so there is nothing for you to run locally to make them work.
A direct line to USPS, on your own terms
Aggregators are the easy way in, and they are a good answer for a lot of stores. But if you already hold a USPS business account, going through one means giving up the rates you negotiated and adding a margin you did not ask for.
A direct connection means the token is issued to your own application, the CRID and MID on the shipment are yours, and postage is drawn from your Enterprise Payment System account. Nothing is rebilled.
Your account, your contract
The connection uses the USPS app registered to your business. Whatever rates your account has negotiated are the rates you get.
Postage from your EPS account
USPS bills your Enterprise Payment System account directly. Postage never passes through us and we add nothing on top of it.
Credentials encrypted at rest
The consumer secret is encrypted the moment it is saved, kept outside the web root, and never shown again — not to you, not to us.
Nothing to run yourself
USPS refuses a lot of ordinary server traffic outright. We handle that end, so the connection works from the platform without you hosting anything.
We check it and tell you
We verify the connection from our side and tell you exactly what USPS says — including which API products your app is still missing.
Runs beside Royal Mail
Selling both sides of the Atlantic is normal. A store can hold a USPS connection and a Royal Mail one at the same time.
Register the app, paste two values
USPS hands out the credentials; you paste them in once. The fiddly part is on the USPS side, and it is worth knowing about before you start.
A token proves the credentials are valid, but says nothing about entitlement — the scope list in the response is USPS's whole catalogue, not your app's. What matters is api_products. An app with none attached returns a perfectly good token and then refuses every call.
Create an app on USPS
At developer.usps.com, register an application and attach the APIs you need — Addresses, Domestic Prices, Domestic Labels and Tracking.
Add an Addresses licence
Since 1 August 2026 USPS gates the Addresses API separately. At cop.usps.com, open My Account then API Licenses and add one.
Paste it into Connections
In your account area, open Connections and fill in the USPS panel: environment, consumer key and secret, CRID, MID and EPS account. Encrypted on save.
What you need
A USPS business account with a CRID and MID, an EPS payment account, and an application registered at developer.usps.com.
How you pay for postage
To USPS, from your own EPS account, at your own rates. It never touches us, and we take no margin on it.
Where this is up to
The connection is live now: you can save your credentials and we will verify them. Rates at checkout and buying labels against an order are being built — this page will say so when they land.
Your store, in plain English
Claude runs the shop through the same tools the admin uses. Shipping is catching up; everything below works on your store today.
Direct, aggregated, or a flat price
There is no single right answer here. It depends on whether you already hold a USPS account worth using.
| USPS direct | Via EasyPost | Flat rate shipping | |
|---|---|---|---|
| Whose rates you get | Your own negotiated contract | The aggregator's carrier rates | Whatever you guessed |
| Carriers covered | USPS only | USPS, UPS and FedEx | Any, if you pick right |
| Accounts to set up | USPS business account, CRID, MID and EPS | One key | None |
| Who bills the postage | USPS, to your EPS account | The aggregator, to your account | Nobody — you absorb it |
| Margin added on top | None | The aggregator's | None |
If you do not already hold a USPS business account, an aggregator is very likely the easier start — see the EasyPost page. Direct is worth it when the contract you have beats what you would be given.
USPS on Claude CMS — common questions
Do I need my own USPS account?
Yes. This is a direct connection to USPS using an application registered to your business, which is the point of it — you keep your own rates and your own contract. If you do not have a USPS business account, an aggregator such as EasyPost is the easier way to start.
Where do I find the consumer key and secret?
At developer.usps.com, open the application you registered. They are shown as the Consumer Key and Consumer Secret. Paste them into the USPS panel in Connections — the secret is encrypted as soon as it is saved and is never shown again.
My credentials are accepted but every call is refused. Why?
Almost always because no API products are attached to the application. USPS will issue a perfectly valid token for an app with no entitlements at all, so the credentials look correct while every request comes back 403. Open the app on developer.usps.com and add the APIs you need — Addresses, Domestic Prices, Domestic Labels and Tracking.
The token response lists dozens of scopes. Doesn't that mean I have access?
No, and this catches people out. The long scope string is the catalogue of everything USPS offers, not what your application is entitled to. The field that matters is api_products. If it reads only "Default Access", nothing is attached yet.
Addresses calls fail even though I attached the product.
USPS introduced separate Addresses API Access Controls on 1 August 2026. As well as attaching the product, you need a licence on the account: at cop.usps.com, go to My Account, then API Licenses, then Add an Addresses API License.
Rate calls mention "contract information is not authorized". What is that?
It reads like a bad request but it means no payment account is linked to the application. Link your EPS account, CRID and MID to the app and the rate calls start working.
What are CRID, MID and EPS?
The CRID identifies your business to USPS, the MID identifies you as a mailer on the label, and the EPS account is what postage is drawn from. All three come from the Business Customer Gateway, and all three are needed before USPS will price or print anything.
How do I pay for postage?
USPS bills your own EPS account at your own rates. Postage never passes through us, and we take no margin on it. You will need funds on the EPS account before a real label will print.
Can I try it against the USPS test environment first?
Yes. The panel has an environment setting — choose Test / CAT to point at USPS's test host instead of production. The credentials are different for each, so use the ones from the matching environment.
Is my consumer secret safe?
It is encrypted the moment you save it, stored outside the web root, and never redisplayed — leaving the field blank when you edit keeps the stored value. We never send it back to your browser or put it in an email.
Can I use USPS and Royal Mail on the same store?
Yes. They are separate connections and a store can hold both, which is the normal setup if you post from the US and the UK.
If it has an API, we’ll build the connection
Every other platform answers this question with “is there an app for that?” We answer it by writing the connection. There is no app store here, so nothing has to be popular enough for someone else to build it first, and there is no extra subscription at the end of it.
Your site is your own PHP/MySQL, not a sandbox, so an integration is ordinary server code against the vendor’s API rather than whatever a marketplace app is permitted to reach. Credentials are deposited encrypted in your account area and used server-side only.
Anything with a documented API
Accounting, inventory, CRM, booking, couriers, marketplaces, your own internal system. If it publishes an API, it can be connected.
Built for your workflow
Not the generic version that suits a hundred thousand shops. The one that matches how you actually work, because it is written for you.
No app store, no app bill
Connections come with your plan. No per-app subscription stacking up month after month, and no revenue share on your sales.
Early customers keep this. Connections are included on your plan for as long as you stay on it. If we ever charge separately for them, it will not be for the people who backed us early — you keep what you signed up for.
Tell us the tool and what you need it to do. If it genuinely cannot be done — no API, or the vendor does not allow it — we will say so rather than sell you a workaround.
USPS connects on every store
The Setup + Monthly plan includes the store, the checkout and your connections for one flat monthly price. We never charge per label or take a slice of postage.
- ✓Your own USPS account, your own rates
- ✓Credentials encrypted at rest and never redisplayed
- ✓Connection verified from our side, with the exact USPS response
- ✓Cancel anytime · your account, your contract, your data
No USPS business account yet? EasyPost covers USPS, UPS and FedEx from one key. Shipping mostly within the UK? Royal Mail Click & Drop connects the same way.
Keep the rates you negotiated
Connect your own USPS application to your store, and pay postage from your own account at your own prices.
Get started →