ShippingEasy

I've used this app for years, mostly without trouble, but since I'm on the lowest plan they refuse to provide support even when it's about a bug in their app. No support for bugs means you're dead in the water, and who has time for that. OneBalance Fix for other users: If you need to use funds already in your OneBalance account, you can print your labels directly from Stamps.com. Their interface is clunky but it'll do in an emergency. Your Stamps.com login info is under "One Balance and Carriers", then "Manage Passwords".

After most recent update when using search to fulfill shopify orders shippingeasy has a predictor as you type, sometimes this pulls up the wrong order and I find myself printing the wrong label. This happens way too often and is a real problem!

It's a decently integrated app, but they try to implement too many features and don't do the basics well. Their rudimentary paste and parse address for a quick shipment fails horribly with even the simplest addresses. I've reported this issue several times and still no update after 6 months. A first year programmer could implement this feature more reliably! I would find something better for my complete business shipping solution.

Avoid this company. They want to charge you money to access your own data. You can pay $14 a month and sign up for a marketing app that is tied to it, but overall how it works.
You supply data of customers for shipments.
It wants to charge you to access that data in meaningful report - $14.
Yuck.