Clerk's development instances are great for getting started with Clerk, making local development smooth and simple, and testing out features. However, we have seen many users go to production using their development instance by accident - your app looks exactly the same, and works similarly enough that most wouldn't notice the difference. But if this does happen, it turns into a substantial issue.

Development instances have a more relaxed security posture, are not indexed by search engines, use shared OAuth credentials for social providers by default, and lack custom domain support. In addition, development instances are capped at 100 users, 20 SMS messages, and have "development" prefixes on SMS and email messages, which quickly becomes a large problem if accidentally taken to production. Especially so if the user or SMS limits are hit, which can stop your app from being able to sign up or log in users - certainly not something you want to happen in production 😰. And on top of that, you then need to go through a process of migrating users from your development to your production instance to fix it, which can be challenging and time consuming.

In order to combat this common issue, we made some modifications to the design Clerk's UI components in a specific effort to make it more clear that you're using a development instance. Our hope is that, with these changes, nodoby ends up taking a development instance to production by accident anymore. You can see an example of the change on the <SignIn> component here:

If you need to deactivate this UI change temporarily to simulate how components will look in production, you can do so by adding the unsafe_disableDevelopmentModeWarnings layout appearance prop to <ClerkProvider> as such: