Underdrive

Be at checkout when the drop opens.

Underdrive watches a store product and opens checkout as soon as it can be bought. You review the order and pay. It never pays for you.

Download for macOSVersion 1.0.0 · zip, about 19 MB WindowsComing soon

macOS 12 or later, Apple silicon and Intel. The zip includes a short guide for opening it the first time.

How it works

Underdrive drives a real, visible browser with your own login, so the store sees a normal shopper. You set it up once, then point it at a drop.

1

Set up once

Sign in to the store in Underdrive's own browser window and save Shop Pay there. It's kept apart from your everyday browser, so on drop day paying is one click.

2

Add the drop

Paste the product link, even before the product is live. Choose a quantity and the drop time on your own clock. When the store publishes a per-customer limit or its own opening time, Underdrive shows it.

3

Press Start

Keep Underdrive open and your Mac plugged in. It stops the Mac from sleeping while it waits, and tells you out loud when it's your turn.

  1. Before

    Waiting. Nothing is open yet; the app only needs to keep running.

  2. T − 2:00

    Getting ready. Opens your logged-in browser, loads the product page and checks that the store answers.

  3. Until T

    Watching. Checks stock every 2 seconds but never buys early, even when the item is already in stock.

  4. T

    Drop time. Checks every 400 ms and acts the moment the item can be bought. After 10 minutes it slows down to every 5 seconds.

  5. Your turn

    Checkout. Opens checkout with the item already in it and says “Checkout is open”. You check the order and click Pay now.

T is the drop time you set. These are the default timings; you can change them under Advanced.

Good to know

  • It never pays. Paying stays with you, in the browser window.
  • Do a rehearsal first. Turn on Rehearsal and run it on any in-stock product. It goes all the way to the cart and stops. Nothing is bought.
  • Waiting rooms and captchas are yours to handle. On busy drops the store may queue you or ask for a captcha. The browser is always visible so you can deal with them.
  • Don't close the browser window. Closing it stops the drop. One drop runs at a time.
  • Your login stays on your Mac. It lives in Underdrive's private browser profile, separate from your everyday browser.
  • Use your judgment. Store terms generally frown on automation. Underdrive behaves like a fast person: one item, one session, a visible browser.

First time opening it

Underdrive isn't from the App Store, so your Mac asks you to confirm the first time. You only do this once. The zip also has the full guide, with pictures, as a PDF.

  1. Unzip the download and drag Underdrive into your Applications folder. Open it from there.
  2. Double-click Underdrive. When you see “Underdrive” Not Opened, click Done, not Move to Trash.
  3. Open System Settings › Privacy & Security and scroll down to Security.
  4. Next to “Underdrive” was blocked to protect your Mac, click Open Anyway. Then click Open Anyway again in the box that follows.
  5. Confirm with Touch ID or your Mac password. From then on, Underdrive opens with a double-click.

These steps are for macOS 15 Sequoia and later. On macOS 12 to 14, Control-click Underdrive in Applications, choose Open, then click Open.

There's no need to allow apps from “Anywhere” or to turn off any security setting.

Requirements

macOS
macOS 12 Monterey or later, on Apple silicon or Intel.
Browser
Google Chrome or Microsoft Edge. If neither is installed, Underdrive can download its own private copy of Chrome for Testing.
Windows
Coming soon.