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.
Inside of Form Builder for each text box field you can set Max Size of characters for that field.
I have made demo form with two fields. First field has Max Size of characters set to 5 and second field to 20 characters. Here is my demo form: http://form.jotformpro.com/form/52605695756972?
Hope this will help. Let us know if you need further assistance.