Form Autofill – Unpacking the Magic

Form Optimisation

Complete an online form and your personal details will appear, as Tommy Cooper once said, ‘just like that!’

That’s thanks to browser technology which automatically completes form fields on users’ behalf. It eases the repetitive strain caused by completing the same information over and over again. And Google has found that, used correctly, autocomplete attributes help users finish forms up to 30% faster. We unpack the magic and some the do’s and don’ts that sits behind auto-fill technology.

What Magical Technology Sits Behind Auto-fill?

Most internet browsers include an auto-fill feature; however, each presents a slightly different experience for the user.

There are two main approaches:

1. Chrome and Safari
These browsers have each identified different high-value form fields. They watch the user completing these fields and when they recognise address details, for example, being typed in, they ask the user whether they want to save them for later use.

2. Microsoft Edge and Firefox
These browsers require users to submit a form to allow the browser to store auto-fill values.When a form is submitted, the browsers store the value and associate it with a form attribute, like name. If the browser sees a field in the future with a matching attribute it provides the auto-fill option(s).

The Social Solution

Sign-up forms can also be completed using the data stored in social media profiles. Because social profiles contain most of the information such forms require, multiple fields can be completed with one click.


This can also reduce the number of fields users need to fill in which is good for form conversion rates. Research from web tech business Imaginary Landscape found that forms containing just four fields delivered 160% more conversions.

Particularly Good for Mobile Users

People hate filling out forms on mobile devices. Clicking through multiple pages, pinching screens to fit forms in and trying to find validation errors that pop up off screen. These are all issues that make mobile users quickly abandon forms. Use one-click field completion to reduce user effort and your form will be more likely to convert.

Additional Data Capture

Social profile auto-complete can also deliver additional information, like education, work history and twitter handle, you wouldn’t have otherwise secured.

This can be achieved without social profile data capture. Some organisations complete the majority of fields with data stored from previous visits, but when the visitor returns they pose additional questions to generate further insight. HubSpot is particularly good at this.

How Does Data Appear to Users?

There are many different ways to present the stored auto-fill data in your form. In some instances, fields are already complete. In other cases, the user needs to prompt the auto-fill function. This usually takes place as the user types the first letter or digit at which point the auto-fill kicks in. In some instances, this is on a field-by-field basis, while other forms only require a single click to select the data for all fields.

Sometimes, users are provided with a drop-down menu as they hover over a field; it can provide single or multiple options to choose from.

Source: Matcon IBC

In this instance, the user has a shorter version of their first name to choose from.

Pre-Filled Field Types

Personal Details

Auto-filled fields are many and varied. The most common are personal details that are unlikely to change frequently (or at all) like name, address, email, phone number, date of birth.

Some data provides indicators to likely answers for other questions later in the form. Take title. If an individual says they are a ‘Mr.’, you can code your form to complete the ‘male’ gender field. Another click saved.

Auto-filled personal details are useful for shipping online purchases at which point payment details are likely to be remembered making checkout seamless.

Credit Card Data

With sensitive information, like card details, users are often specifically asked if they want the system to remember them. Amazon is a prime example of how this autocomplete service can interlink with other online technology to make one-click purchasing a common occurrence.

Another trick that saves users a click is to lookup the first four digits of a credit card to identify and auto-fill its type (Visa, Mastercard, American Express etc.)


Although only a very short ‘form’, logging in to platforms is a recurring pain in the fingers. The impossibility of remembering all those usernames and passwords makes autocomplete a godsend.

Similarly to credit card details, users are invariably asked if they want this data to be stored when it’s first entered. However, sometimes, Chrome, Firefox and IE set password autocomplete to ‘on’ overriding HTML coding that requests certain fields are not completed in this way.

While auto-fill passwords make access quick and easy, it does carry serious security risks; if someone bypasses your computer’s security, they can access multiple accounts. Which would make typing in your password seem less of a hassle.

The Dark Side of Auto-fill

Auto-fill on forms can go wrong. Bugs sometimes creep in so the wrong field option data is presented; asking people to select form a list of emails when they really want to add in a street address is annoying.

For developers, regularly filling out forms with test data means auto-fill can get in the way. Which is why it’s often the last thing to be tested or, in some cases, is not checked at all. But testing is important; as our case study shows, broken auto-fill increases drop-off rates.

The efficiency that auto-fill can bring is unquestionable. But correctly implementing privacy settings and background storage is critical. Get it wrong and assume people want their personal details stored and some users might find it an invasion of privacy or a little creepy. Get it right and you’re well on your way to quicker, simpler form completion and more conversions.

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