This plugin hasn’t been tested with the latest 3 major releases of WordPress. It may no longer be maintained or supported and may have compatibility issues when used with more recent versions of WordPress.

Formstack Online Forms


Formstack’s WordPress form plugin makes it quick and easy to embed contact forms, lead generation forms, payment forms, and more on your WordPress blogs and websites. Build customized online forms in seconds with our drag-and-drop interface, and integrate with 40+ third-party apps, including Salesforce, MailChimp, and PayPal.

This plugin features two components:

  • Formstack Widget
  • Formstack Plugin

The Formstack widget allows you to embed Formstack web forms into your sidebar. The widget automatically optimizes the web form’s CSS to make your online forms fit and look great on your WordPress pages.

The Formstack Plugin adds a button to the TinyMCE editor that allows you to easily select the Formstack web form you wish to embed. Once a form is selected, a shortcode will be inserted into the editor, which will be converted to the selected form once your page or blog post is rendered.

This plugin supports the following shortcodes [Formstack], [formstack], and [fs].

A Formstack account and API key are required. Signup for free today!


  1. Download the plugin zip file by clicking “Download” in the upper right corner of the page.
  2. Upload via the Upload link in the WordPress plugins dashboard.
  3. Activate the Formstack Plugin through the “Plugins” menu in WordPress.


Where can I find my Formstack API key?

Your Formstack API key can be found in your account settings. Go here
to find or create your API key:


Janairu 26, 2022
For a system that asks a lot of money for their service, you would think they would keep their features up to date. Nope. Can’t use this plugin, it just errors out. Can’t even use their embed javascript because you get a 403 server error.
Aprailu 4, 2019
It seem like you guys are trying to do too many things, but nothing works properly. Signed up with Formstack, your Drupal extension doesn’t work, this WordPress extension doesn’t work either. It sends people to Formstack for confirmation instead of staying on the same page. This plugin hasn’t been updated for 2 years. .. wtf! The only thing I’m stuck with are iFrames. These suck, but at least work. Get a grip guys. You charge a lot of money for your service.
Nuwamba 2, 2017 12 replies
Form cache can be refreshed immediately to pull in new forms rather than wait an unknown period for the new form to appear in your list. With 300+ forms the old plugin was quite slow, this one loads the forms from a cache, thus loads relatively immediately compared to the APIv1. Overall huge improvement. I would have given it 4/5 stars because the forms aren’t ordered, but Michael who made the plugin is amazing and provided a workaround via the support thread. Quite easy fix with roughly 4 lines of code (not sure why they haven’t pushed the changes as 2.0.2). Formstack is a great product overall, integrating with major players. If I had to give a cost to formstack in general (not the plugin) higher than average cost would be the biggest drawback for most small businesses. Ignore the 1 star reviews, this plugin works just fine if you can handle 5 minutes of setup.
Satumba 8, 2017 2 replies
The previous plugin worked fine. This won’t authenticate and won’t allow me access to my forms. When saving new API and client ID it gives me this: Warning: Invalid argument supplied for foreach() in /home2/ogom/public_html/wp-content/plugins/formstack/plugin.php on line 288 Warning: Invalid argument supplied for foreach() in /home2/ogom/public_html/wp-content/plugins/formstack/plugin.php on line 288 Warning: Cannot modify header information – headers already sent by (output started at /home2/ogom/public_html/wp-content/plugins/formstack/plugin.php:288) in /home2/ogom/public_html/wp-includes/pluggable.php on line 1210
Satumba 3, 2016
From Formstack’s own website… “compatible with up to WordPress 4.0” It wants you to use Formstack’s API v1 which is now deprecated and discouraged BY FORMSTACK! Do not install this plugin!
Satumba 3, 2016
I’m not sure wrapping if this is just this version or all versions, but wrapping your site in an iframe doesn’t constitute as a functioning plugin. Doesn’t work on WP 4.5 as far as i’m concerned.
Read all 8 reviews

Contributors & Developers

“Formstack Online Forms” is open source software. The following people have contributed to this plugin.




  • Fixed: Errors with unauthenticated accounts and trying to use API in widget.


  • Fixed: Adjusted timeout value to 120seconds for API requests to accommodate for large responses.


  • Added: Embed options when choosing a form. Conditionally include jQuery, jQueryUI, Modernizr, and Formstack-provided CSS.
  • Added: options to clear/refresh cached Formstack lists in your WordPress admin.
  • Updated: Make the plugin use Formstack API V2 API over the older V1.
  • Updated: Removed the embedding of Formstack account admins within WordPress admin page.


  • Increased timeout limit for API requests.
  • Conditionally loading content meant for TinyMCE.
  • Added caching for API requests. Will especially help those who have large amounts of lists.
  • Improved handling of cases where API requests return no lists.


  • Fixes js bug with empty forms array when inserting form into post.


  • Reworked and updated plugin to current WordPress standards
  • Confirmed compatibility with latest WordPress versions.


  • Update compatibility reference for 4.2


  • Update compatibility reference for 4.1


  • Resolve issues with the Widget in WordPress 3.9
  • Resolve issues with Widget when no API Key is saved for the Plugin


  • Fix incompatibilities with Worpdress 3.9


  • Formstack side-menu now properly links to appropriate Formstack
  • functionality, no longer hardcoding embedded forms’s version


  • Formstack side-menu now defaults to the bottom (instead of possibly over-writing an existing menu).


  • Increased functionality, build forms within WordPress, better error messages


  • Added PHP version to the options page for easier troubleshooting.


  • Added Formstack API status area on the plugin settings page.


  • Now using wp_remote_fopen for improved server compatibility. Should fix errors some people were having when loading the widgets page.
  • Minor housekeeping


  • Hello World