What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
If you will use the "Address" field found under the "Quick Tools" section, there's no option to validate the value of the zip/postal code.
If you'll use a simple text box, that allows you to set or impose a validation type and an input mask, you can also set max size and a default value. You can also use conditional logic to check if the value inputted is valid in your own terms.
We also have widgets related to geolocation or postal codes. Here are some of them:
I hope that helps.