If you’re a Wufoo power user, you probably know that you can use our [URL Modifications API](https://help.wufoo.com/articles/en_US/kb/URL-Modifications/) to design URLs that will prefill your form with data contained in the link format. For example this URL:
Will link to a form with the name field already filled out. While this is a really powerful feature, we are aware that it’s a smidgen nerdy. You have to understand a lot of concepts to get the URL structure right and if you want to use it to prefill a lot of fields on your form or change it regularly, it can be fairly difficult to maintain.
Thankfully there is a great little third-party web application called [Wufood](http://wufood.heroku.com/), which was designed by the guys over at [Lucid Design](http://luciddesign.co.nz/), that can help automate generating those complex links. Wufood allows you to see all the fields on your form, fill out the ones you need prefilled in a really straightforward manner, and then give you the URL in exactly the right format.
To get started, you’ll just need two bits of information: your **subdomain** and your **API key**. Your subdomain is your account name. Easily findable by literally looking at the word that comes before wufoo.com in the URL when you are logged in. For example, in `http://monkey.wufoo.com`, the subdomain is **monkey.** Your API Key can be found by going to the Forms tab, then clicking the **Code** button beneath your form, and then the **API Information** button in the upper right hand corner.
On [Wufood](http://wufood.heroku.com/), just enter these two fields and click the button. You’ll then see a list of all your forms. Choose the form you wish to prefill, and all the fields from that form will display below. This is where you enter all your prefill values.
In the screenshot example below, we’ve created a link to a **Donation Form** we are going to send to Bob Johnson. The form will be prefilled with Bob’s name, email address, and a suggested donation amount.
Since we’re asking ol’ Bob for money, shouldn’t we make it as easy as possible for him? Here is the completed URL:
Wufood also provides a [Bit.ly](http://bit.ly/) URL, which is a **shortened** version of the final URL. Prefill URL’s can be very long and not very pleasing to the eye, so using the shortened version can help there. Not to mention that the shortened URL will be much easier to share on services which limit the length of your messages like [Twitter](http://twitter.com/wufoo).