Installation

Published on: January 2, 2026

Last updated: January 10, 2026

M Media USPS OAuth Shipping installs like a standard WooCommerce shipping plugin, but there are a few important sequencing steps. Follow this guide in order to avoid authentication errors, missing rates, or zone misconfiguration.

If you are migrating from an older USPS plugin, do not remove your existing shipping methods until this plugin is installed, activated, and returning rates successfully.

System Requirements

  • WordPress: 5.8 or higher
  • WooCommerce: 5.0 or higher
  • PHP: 7.4 or higher
  • USPS Business Account: Required for API credentials

Note: Shared hosting is fine, but outbound HTTPS requests must be allowed. If your host blocks remote API calls, USPS rates cannot be retrieved.

Step 1: Install the Plugin

  1. Download the plugin ZIP file.
  2. Log into your WordPress admin panel.
  3. Go to Plugins → Add New → Upload Plugin.
  4. Select the ZIP file and click Install Now.
  5. Once installed, click Activate.

After activation, the plugin registers itself as a WooCommerce shipping method but does not affect checkout until configured.

Step 2: Verify WooCommerce Basics

Before entering USPS credentials, confirm the following:

  • Store address is set (WooCommerce → Settings → General).
  • Currency is correct.
  • Shipping is enabled in WooCommerce.

WooCommerce uses your store address as the shipping origin unless otherwise specified.

Step 3: Enter USPS API Credentials

  1. Go to WooCommerce → M Media USPS.
  2. Enter your USPS Client ID.
  3. Enter your USPS Client Secret.
  4. Set your Origin ZIP Code.
  5. Choose whether to enable Sandbox Mode.
  6. Click Save Changes.

Important: Sandbox Mode must match the credentials you are using. Test credentials require Sandbox Mode. Live credentials require Sandbox Mode to be off.

Step 4: Test the USPS Connection

On the plugin settings page, click Test Connection.

  • If successful, you will see a confirmation message.
  • If it fails, do not proceed until this test succeeds.

Most connection failures are caused by credential approval status or sandbox/production mismatches.

Step 5: Add the Shipping Method to a Zone

  1. Go to WooCommerce → Settings → Shipping.
  2. Edit an existing shipping zone or create a new one.
  3. Click Add shipping method.
  4. Select M Media USPS OAuth Shipping.
  5. Click Add shipping method.

The plugin will not return rates unless it is attached to at least one shipping zone.

Step 6: Configure Zone Settings

Within the shipping zone method settings:

  • Enable the method.
  • Select which domestic and/or international USPS services to offer.
  • Optionally set a handling fee.
  • Optionally set a rate adjustment (markup or discount).
  • Optionally set a fallback rate for API downtime.

Step 7: Verify Product Data

USPS rates require accurate product data:

  • Each shippable product must have a weight.
  • If products lack dimensions, configure Default Dimensions in plugin settings.

Missing weights are the most common reason rates do not appear.

Final Validation

Before going live:

  • Add a test product to cart.
  • Enter a valid shipping address.
  • Confirm USPS rates appear at checkout.
  • If testing, repeat with Sandbox Mode enabled.

Once rates are visible and accurate, installation is complete.

If you encounter issues at any step, see the Troubleshooting section before contacting support.

// real.developer.js
const approach = {
investors: false,
buzzwords: false,
actualUse: true,
problems: ['real', 'solved']
};
// Ship it.

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✓
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