Improving mobile design for your forms with CSS

123FormBuilder forms work great on all mobile devices and tablets and offer a user-friendly experience on any device.

Our forms are by default mobile responsive, however, you can tweak your existing web forms design with our CSS form generator. In this article, we will show you a step-by-step guide on how to accomplish that.

Form Images

When you insert an image in the Form Header or HTML blocks you will need to specify the best settings to ensure that it will be mobile responsive. In the editing mode of your HTML field click the plus sign and select Image.

Form header image

After you upload the image, in the Dimensions section, type 100% in the first box (width) and auto in the second one (height). Disable the Constrain proportions option to maintain the original width and height dimensions.

Edit image


When you add an iframe to display a video you can use a custom CSS code to make it work perfectly for mobile devices. The CSS will be placed in the DesignAdd Custom CSS section. This method applies to all iframes. Simply copy-paste the code from below:

height: auto;
width: 100%;

Custom CSS

Font Size

Font size may seem like a small thing, but it is an important element, especially for mobile readers. You can use the following CSS and adjust the number of pixels (12).

@media only screen and (max-width: 550px) {
#form *{
    font-size: 12px!important;

Submit Button

Enlarge the submit button to have better visibility. The CSS code from below will make the submit button wider.

@media only screen and (max-width: 550px){
#form button[data-role] {
padding: 0px 33%;

Decrease the percentage number if you want the submit button to be more narrow or increase the number (33%) to make it wider.

Form button mobile design

To make the font size of the submit button smaller simply adjust the number of pixels.

@media only screen and (max-width: 550px){
#form button[data-role] {

That’s it! Now your forms are fully mobile responsive and form visitors will have the best user experience with these design tips.

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Frequently Asked Questions

Here is a list of the most frequently asked questions. For more FAQs, please browse through the  FAQs page.

Is this service free?
Yes, we offer a free form builder service. Just sign up to the Basic plan and you are all set. This plan is forever free, but you are limited with a few features only, such as 5 forms per account, 100 submissions per month and you have to keep the backlink to 123FormBuilder on your forms. Check out our features matrix for more information.
How many forms can I create?
It depends on the service plan you are on. Higher service plans enable more features, including more web forms for your account. If you need more forms, go to the My Account section of your account and click the upgrade button. To create an unlimited number of forms, either upgrade to the Platinum service plan or higher. Consult our features matrix for more information.
How can I publish my forms?
You can publish your forms in many ways, by using their direct URL or HTML link, embedding them with a JavaScript code, Inline HTML or iFrame, using the Facebook app or the WordPress plugin, using popups, the Blogger code snippet and many more. Once you have created and customized your form, go to the Publish section to complete your work. Read more in our documentation.
How do I change my form design?
You can change the design of your form for more information. in the Themes section, which is located in your form settings. We offer a set of more than 30 predefined form themes for your forms, but you can also create your own from scratch. You can customize the submit button, the logo and more. To apply your own stylesheets, all forms come with a custom CSS editor.

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