Zuko Blog

Does using browser autofill affect form conversion rate?

Data showing whether autofill helps improve the user experience

Earlier this year, Zuko added the ability to track whether users had used the Autofill function in their browser to complete forms. This allowed individual businesses to answer the question of whether autofill was helping or hindering their users to successfully complete their forms.

Now, with a critical mass of forms having been tracked using the technology, we are able to use the aggregated behavioural data to answer this and draw more general conclusions on whether enabling autofill should be part of your form design.

So, is the use of browser autofill related to a user successfully completing the form? This article reveals what Zuko data can contribute to the answer, examines why autofill might (or might not) improve conversion and shares advice on how to use autofill optimally.

What is Browser Autofill?

Browser autofill is that function you see when filling in a webform that automatically completes all relevant fields based on the first interaction you give. Depending on your experience, it can be very convenient - saving you time - or very fiddly - if the automatically completed answers are not correct.

Autofill Example Image
A typical autofill interaction. Source: Google Search Central


For this study, we extracted data from the forms on Zuko’s platform and ran completion analysis on individual forms, looking at the conversion rates of users who started the form and used autofill against users who started but didn’t use autofill. We then compared the completion rate and ran a statistical test to check whether any difference in conversion rate was significant (we used the 95% level as a threshold).

The data was then further subdivided into audience groups based on the device type for more granular analysis. We excluded forms which did not have at least 1,000 started sessions for the relevant user group.

We also calculated unweighted arithmetical average completion rates for audience groups (essentially each form was given equal weight).

The Results - Topline

23% of users across the dataset triggered autofill. For these users, the overall completion rate was 71% whilst for non-users it was 59%. However, as these figures will be skewed by the highest traffic forms, in order to get the full picture we need to look at the form level breakdown. This is outlined in the below table.

Total Forms Analysed      215
Forms where autofill users had significantly higher conversion rate 160
Forms where autofill users had significantly lower conversion rate 24
Forms where the conversion rate between autofill users & non users was not significantly different 31

Source: Zuko Database

From this dataset, it appears that, generally, autofill is positively related to users successfully completing forms. However, there is still a non-negligible minority of forms (c. 10%) where users triggering autofill is negatively related to completion - essentially users who trigger autofill are less likely to convert.

The Results - Segmented

The user experience of forms in the mobile environment is very different to the desktop environment. To be sure of our conclusions, it’s important to segment these groups to assess whether either of them is overly affecting the general result.

The arithmetic averages (below) show that desktop users have slightly higher conversion rates across all groups than mobile users but the difference is not huge.

Desktop Mobile
Average Completion Rate 62% 60%
Average Triggered Completion Rate 72% 71%
Average Non-Triggered Completion Rate 59% 57%

The form level breakdown has similar results to the overall data in that the majority of forms had a positive relationship between autofill interactions and completion. There also remains a non-trivial segment of forms where the reverse is true.

Desktop Mobile
Total Forms Analysed 153 162
Forms where autofill users had significantly higher conversion rate 104 116
Forms where autofill users had significantly lower conversion rate 21 19
Forms where the conversion rate between autofill users & non users was not significantly different 28 27

Source: Zuko Database. Note the different number of forms analysed is due to the 1,000 started session cut-off.

The broad conclusion from this data is that users of autofill are generally (but not exclusively) more likely to complete forms than those who don’t use autofill.

But why is this?

Why does autofill help completion rates?

The simple answer to this question is that autofill speeds up the form filling process, reducing cognitive load so reducing the opportunities for the user to get bored, annoyed or distracted enough that they fail to complete. Zuko isn’t the only study that backs this up. Chrome published research suggesting a 25% increase in form completion when autofill was enabled.

However, the truth is probably a little more nuanced.

As well as time saved, there are other positive factors at play:

Errors - If a customer has the correct information saved in their browser, and you have coded your form correctly, errors due to typos should be eliminated. Even the simplest error message can trigger the production of cortisol and the stress response, negatively impacting the user experience. Removing the possibility of these errors eliminates one potential point of friction.

User self selection - This is still a hypothesis at this stage but the reasoning goes that form visitors who consciously use browser autofill are already predisposed to completing the form. They are more sophisticated users who have entered autofill information previously so they know what they are doing and why. Users who don’t trigger autofill may be more tentative; they don’t want to get sucked into completing the form - the non-use of autofill is an indicator of low conversion intent. This scenario would mean that correlation does not mean causation - the use (or not) of autofill is a measure of intent rather than a driver of conversion.

Why might it hinder conversion?

The analysis shows that autofill is not always a one way bet. There were forms which converted at lower rates if it was triggered. Why might this be the case?

The most likely explanation is poor implementation of autofill itself or the validation of the answer + the associated error messages.

It is not uncommon that, when using autofill, the wrong information is input into each field. This is generally because the autofill has been coded incorrectly or it has been left for the browser to guess the correct input based on HTML ‘name’ or ‘id’ rather than ‘autocomplete attribute’ (see later for more details on this) so, for example, a ‘First Name’ field inputs the whole name or the home address is used to fill in the ‘Billing Address’ field. These incorrect inputs are often not spotted by the user until they click submit. The frustration of a sea of red error messages appearing when they trusted that autofill had done its job causes them to abandon.

In addition, not all fields may have associated autofill data. The visitor may jump ahead, assuming the form is complete only to find they have missed something and they have to return.

Linked to these points is the execution of error messages themselves. If an input error is picked up immediately through inline validation then the user can pick it up and correct it quickly. If that error is ignored until the submit then, in the worst cases, the user may not even be able to identify where they have made a mistake and will be bobbing up and down the form to try and find the issue. Always make sure that errors are triggered immediately after input to minimise UX pain.

Finally, on certain forms, autofill can disrupt postcode look up functions on the page. If you are not careful, you can end up with a hot mess of menus like this:

Source: Webtrends Optimize

Tips for enabling browser autofill

Given that well executed autofill is likely to smooth the user journey towards successful form completion, how do you make sure that it works as it should?

By far the most important factor is to make sure you have coded the field attribute correctly so that the right answer is pulled from the browser. The below image shows the most common HTML autocomplete attributes. You should use these standard versions rather than trying to create your own.

Autocomplete attributes
Source: Google Developers

Other things to be careful about are:

As a practical example; to annotate a Zip Code field correctly you can do something like this

<input type="text" name="zip-code" id=”zip-code” autocomplete="postal-code">

In summary, autofill can be a powerful tool to improve your form conversion rate as long as you follow the standard guidelines and make sure that each field is annotated correctly with the autocomplete attribute. If you'd like more advice and insight on improving the UX of your forms, take a look at our free Guide to Form Analytics and Optimization.

Or, if you're keen to understand how to use data to improve your forms, download our specialist guide to doing just that.

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More from our blog:

Optimizing the phone number field on forms
UX tips to reduce abandonment on mobile and landline form questions
Form UX Design Tips: Best Practice Examples
10 form design patterns that help optimize conversion
8 Tips to optimize your mobile form UX
CRO advice for forms on mobile devices
Lead Generation Form Design: Advice & Best Practice
Tips on creating a high conversion lead capture form

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