Plugins and links / OpenCart

OpenCart

Adds Pay with USDC or USDT to the OpenCart checkout. The customer pays on the Mintage Pay payment page and the order moves to Processing by itself when the payment is final.

Tested on 5 October 2026 with OpenCart 4.0.2.3 and OpenCart 3.0.4.0 against the sandbox: install, connect, checkout, payment, order updated without the customer returning to the store, and removal.

What you need

OpenCart 4.0.x or 3.0.x. The version is shown at the bottom of the admin page.
An admin account that can change Extensions.
The customer's currency must be one Mintage Pay supports: USD, EUR, GBP, CAD, AUD, CHF, JPY, MXN, BRL, INR, SGD, AED, PLN, SEK, NOK, DKK, NZD, ZAR, TRY, KRW, HKD, NGN, ARS, PHP, IDR, VND, PKR, EGP, BDT, KES, GHS, TZS, COP, CLP, PEN, UYU, PYG, BOB, DOP, GTQ, CRC, THB, MYR, TWD, LKR, NPR, KZT, UAH, ILS, SAR, QAR, CZK, HUF, RON, ISK, XAF or XOF. The method is hidden for other currencies. Your customers always pay in US dollar stablecoins: a price in another currency is converted when they check out.
Your store on https, reachable from the internet. Maintenance mode blocks payment updates.
A Mintage Pay account with at least one payout address set.

Download

Your version	File
OpenCart 4.0.x	mintagepay.ocmod.zip for OpenCart 4
OpenCart 3.0.x	mintagepay.ocmod.zip for OpenCart 3

Do not rename the file. It must be called mintagepay.ocmod.zip when you upload it: OpenCart names the extension after the file. If your browser saved it as mintagepay.ocmod (1).zip, rename it back first.

Install on OpenCart 4

Go to Extensions > Installer, click Upload and choose the file. Then click the green Install button on the Mintage Pay row.
Go to Extensions > Extensions and choose the type Payments. Find Mintage Pay (USDC / USDT), click Install, then Edit.
In the Mintage Pay dashboard, open Developers > API keys and create a key. Copy it: it is shown only once.
Paste the key. Choose the order statuses (the usual choice: waiting for payment = Pending, paid = Processing, on hold = Pending, cancelled = Canceled). Set Status to on.
Click Save. The page says Saved. Connected to Mintage Pay as (your business name). Webhook registered.

Install on OpenCart 3

Go to Extensions > Installer, upload the file and wait for the progress bar to finish.
Go to Extensions > Extensions and choose the type Payments. On Mintage Pay (USDC / USDT), click Install, then Edit.
Paste the key, choose the statuses and set Status to Enabled, as for OpenCart 4. Save.

Leave API base URL empty. The key decides where the extension connects.

If saving shows an error

Message	What to do
"did not accept the API key"	The key is wrong or was revoked, or it is a live key in a sandbox setup
"webhook could not be registered"	The store must be on public https
"could not be reached"	The server cannot make outgoing https calls. Ask your host

Try it first with test money

Create a free account at sandbox.mintagepay.com, set a payout address and create a key there.
Paste the sandbox key in the extension settings and save.
In the storefront, add a cheap product to the cart and go to checkout. Choose Pay with USDC or USDT and confirm the order. You land on a payment page with a Test mode banner. In the admin the order is Pending.
Pay on the payment page with free test money. The page has a button to get some.
Within a minute or two the order is Processing, with a history entry giving the amount and a link to the transaction.
When you are happy, paste your live key and save.

If an order stays Pending after it was paid

Look in System > Maintenance > Error Logs. A line with "invalid_signature" means the stored secret does not match: tick Register the webhook again on save in the extension settings and save.
No line at all means the update did not arrive. Check https, the firewall and maintenance mode.

Update to a new version

Download the new file for your version (same name, mintagepay.ocmod.zip). Your settings, your connection and the link between your orders and their payments are kept. An order that was waiting for payment when you updated is still marked paid when the payment arrives.

OpenCart 3: in Extensions > Installer, upload the new file. It replaces the old one.

OpenCart 4 does not accept a file for an extension that is already installed. Use one of these:

Replace the files. Unpack the zip and copy its contents over the folder extension/mintagepay/ on your server (SFTP or your host's file manager). Nothing else changes.
Without server access:
1. Extensions > Extensions > Payments: click Uninstall on Mintage Pay. This switches off the connection and removes the settings.
2. Extensions > Installer: click Uninstall, then Delete, on the Mintage Pay row.
3. Upload the new file and click Install.
4. Extensions > Extensions > Payments: click Install on Mintage Pay, then Edit, paste your API key again and save.
Do this at a quiet moment: between steps 1 and 4 your store is not connected.

The settings page shows the version at the bottom of the note about currencies.

Remove the extension

In Extensions > Extensions > Payments, click Uninstall on Mintage Pay. This switches off your store's connection at Mintage Pay and removes the settings.
OpenCart 4 only: in Extensions > Installer, click Uninstall and then Delete on the Mintage Pay row.

Your past orders keep their link to their payments.

Last updated 25 October 2026. This page as Markdown. Something missing or wrong? Write to hello@mintagepay.com.