Build a Smarter Signup Flow with ZeroBounce + Supabase Auth on Lovable Cloud

Say goodbye (for good!) to invalid emails, disposable signups, and user typos. This guide shows you how to build a smarter, cleaner, and fully validated signup flow using ZeroBounce, Supabase Auth, and Lovable Cloud, without adding friction for your users.

When you build anything that requires user signups – from a SaaS app to a startup Minimum Viable Product (MVP) – you understand the huge role of your email list is. But you must remember that not every signup is valid:

• People mistype their addresses
• Bots can flood your forms
• Disposable emails sneak into your email database. 

These issues are more common than you think. And here’s the thing: there’s a cleaner, faster way to stop all of that bad data at the door.

It’s not that difficult to integrate ZeroBounce’s real-time email validation into your Supabase Auth workflow using Lovable Cloud. It’s an open-source, plug-and-play way to improve email deliverability, reduce bounce rates, and keep your user database squeaky clean.

GitHub Repo: ZeroBounce + Supabase Auth Integration (Lovable Cloud Guide)
Remix on Lovable (and build it in minutes)

Why email validation matters to your signup flow

Your app’s signup form is where a lot of customer journeys begin. However, not all connections are equal. Without email validation, your CRM can rapidly become polluted with bad data.

That’s where using a validation service like ZeroBounce makes a big difference. Using a  real-time email validation API will instantly identify:

• Undeliverable email addresses
• Invalid email addresses
• Disposable or temporary emails
• Spam traps and abuse addresses
• Everyday typos 

When you combine ZeroBounce with Supabase Auth for authentication and Lovable Cloud to allow rapid deployment, you can create a smart signup system. You’ll filter out harmful data before it can infect your database.

Try the ZeroBounce real-time email verifier

Let’s build your signup flow

In this integration, you’ll set up a production-ready signup flow. It will do the following:

• Automatically validate every new email signup
• Show instant feedback if an address looks invalid
• Suggest corrections for typos like gmial.com ? gmail.com
• Block disposable or suspicious emails 

This is made possible with a simple SQL migration, a ready-to-use React form, and your ZeroBounce API key.

Getting started in Lovable Cloud

Lovable Cloud is the AI-powered fullstack app builder for Supabase and Next.js and is perfect for setting up this integration in minutes.

Step 1. Upload the two files

In your Lovable chat, upload:
zb_migration.sql
example_auth_form.tsx

Next, you’ll write this prompt:

“You are my senior engineer programmer. I’m attaching two files:

zb_migration.sql example_auth_form.tsx

Plan

First apply the migration. Then implement a production-ready user signup flow in this repository using the attached files as the source of truth. Make minimal, idiomatic changes that fit the project’s existing stack and conventions.”

With this single prompt, the Lovable agent applies your database migration and connects the frontend automatically.

Step 2. Add your ZeroBounce API key

You must enable Cloud Mode in Lovable, then open your Supabase database.

Go to Cloud ? Tables ? app_secrets, and insert a new row:

name	value
ZEROBOUNCE_API_KEY	your_api_key_from_zerobounce.net

You can find your API key here.

Now your Cloud backend could securely connect to ZeroBounce’s validation API.

Step 3. Try the signup flow

Preview your Lovable app and try it out by signing up with a few test emails:

• Typo example: jane@gmial.com ? “Did you mean jane@gmail.com?”
• Disposable email ? instantly rejected
• Valid address ? signup should complete successfully

The best part? All of this happens in real time, powered by Supabase triggers and stored functions from the zb_migration.sql file.

Try our free email tools

Behind the scenes: how it works

Are you curious about how all of this works? Let’s take a look at what’s happening under the hood:

1. The user submits their email in the signup form.
2. Supabase runs a trigger (before_auth_user_insert_validate_email).
3. That trigger calls ZeroBounce’s /validate API using the key you’ve stored.
4. If the result is invalid or risky, the signup will be blocked immediately and automatically.
5. Validation logs are stored in the zb_email_validation table for review or analytics.
   
6. The frontend will display friendly feedback using toast notifications.

And what is the end result? You’re collecting only valid, high-quality emails. Your emails are verified without adding friction or unnecessary steps for your users.

Code overview

zb_migration.sql

This file configures your backend for validation. It:

• Creates app_secrets (for API key storage)
• Creates zb_email_validation (log table)
• Adds triggers and Supabase functions
• Integrates seamlessly with auth.users

Quick tip: For extra protection, consider moving validate_email_with_zerobounce to an Edge Function for rate limiting or using our JS Widget Integration

 example_auth_form.tsx

A production-ready signup form component built with:

• React + TypeScript
• Supabase Auth
• shadcn/ui for a clean, modern style

Watch the walkthrough tutorial

You can watch the complete step-by-step video on connecting Supabase, applying the migration, and testing real-time validation – all in action.

Why it’s worth improving your signup flow

Building your signup flow is about more than a smooth UX: it’s about securing your data quality and upping email deliverability. Every invalid or low-quality email that slips into your database has the potential to create interruptions. 

If your onboarding emails bounce, your nurturing and other sequences miss real customers who need them. Even worse, your sender reputation starts a downward spiral. The result is that even all of your legitimate messages start missing the inbox.

That’s why validating each and every single email address immediately at the signup makes such a difference. 

If you use ZeroBounce, Supabase Auth, and Lovable Cloud together, you’re doing more than blocking innocuous typos. It’s more than that because you’re setting up a system that quietly strengthens every part of your email ecosystem and related channels. 

What’s more, you can simplify things with a package like ZeroBounce ONE. You’ll get a handle on data quality by putting the email validator to work. And you’ll get access to ZeroBounce’s entire suite of email deliverability tools – from blacklist monitoring to email warmup – if you want to take your email outreach to the next level.

Your reach, growth, and trust rely on it. The great thing is that once you’re all set up, it starts paying for itself. You’re ensuring that you only deal with clean, verified, high-quality data. That’s the only data that matters.