How do I make it so my users can't add any special characters in their usernames?

[Robert_Petitto]

You’ll need to use what we call a “custom form” (not a form screen) to check if they’re entering special characters. I might actually use a “hybrid form” for this.

Radar Address Complete in Form

What I’ve been doing lately is to use what I’m calling “hybrid” forms: show new screen action instead of form screen add an input component for any input you want to validate against another table (using relations, etc) add a form container beneath the input for the remainder of the form, but only display the form container if the input outside of the form container is “valid”. This way you still have a form experience with less updates but can still leverage the custom form experience for th…

You can check for special characters using either a JavaScript or extract matching text column.

I’ll see if I can find an example of something I did recently.