Preorder, Back In Stock ‑ Stoq

They are a small team of 3 working full time on building Shopify apps & supporting merchants.

The live chat support was fantastic. They respond quickly and had no problem resolving issues I had with customizing the button and pop up to match my theme.

INSTALL THIS APP.
Wish I could give more than 5 stars! Our theme was automatically inserting an out of stock form with nearly no functionality...it only sent us email notifications which required us to manually respond to when back in stock... (that's not good enough!) We wanted something automated and found Restock Rocket... It offers powerful features, extensive customization options, and the back in stock notification emails come from YOU, not a third party server, so it's far less likely to land in your customer's spam folder. The developer is a one-man team: Kartik. I don't think he even sleeps! We did have a few questions that we submitted at odd hours, and he always responded within seconds (not an exaggeration... he is so nice, knowledgeable, and helpful). I cannot recommend highly enough!!! INSTALL THIS APP. PS if your theme automatically inserts its own out of stock form that you need to disable, this link was how we turned ours off... yours might have a similar switch to turn it off so that the Restock Rocket app takes over.
https://help.outofthesandbox.com/hc/en-us/articles/115013035567-How-Does-the-Back-in-Stock-Notification-Form-Work-

Great app! Super easy to use, styling is great and the customer service is excellent. Highly recommend!

What is ideal about this app is having both SMS and Email fields in the same sign-up widget. Thank you Kartik for your support, especially on a Sunday!

This app is fantastic. Within an hour after installation, I had already received several sign ups for back in stock notifications. AMAZING!!! The app has some great features which allows you to customise messages, buttons etc. to fit in with your brand look, feel and tone of voice. The app was easy to install, Kartik was on hand to give assistance if needed. The customer service was professional and prompt. You can be up and running within minutes with this app with no coding required, which was a HUGE PLUS. Did I mention this app is free? Yes all this is free! If you need a no-fuss restock app, don't bother to look any further. This is it!

Very good Product support, very easy to use and pleasing interface :)

Really helpful customer support. App seems to work great and was fairly easy to set up. Overall great experience so far.

We switched from a different app because of issues and I had this set up in just a few minutes. Messaged support because the button wasn't showing up on all pages and Kartik had it resolved for me in just a few minutes. Looking forward to digging into the reporting as our customers sign up for notifications.

Amazing app! So easy to configure plus any additional edits were supported by the customer service team immediately and efficiently.

Great and easy to use app. Also a great service. We had an issue to install the app because we use a custom theme. Katrik helped us very quickly and now it is running.