The phone number field is not what's killing your form
Every article says remove the phone field because it destroys conversion. The largest published dataset says otherwise. The gap between those two is where the money is.
The signal
A phone number field is one of the highest-abandonment inputs on web forms, and when it is required without explanation, most of the numbers collected are fake.
Every article about the phone number field says the same thing: remove it, because it destroys conversion. That advice is roughly right and precisely wrong, and the difference costs you either leads or data depending on which way you get it wrong.
The evidence is messier than the headlines suggest. One documented test lost 36.9% of signups by adding a phone field that was not even required. Meanwhile the largest published dataset on form field abandonment shows the phone field performing about as well as an email field, most of the time. Both are true. The gap between them is where the money is.
Is the phone number field costing you on your form?
Check four things on your main form: whether a phone field exists, whether it is required, whether any text explains why you need it, and what percentage of the numbers you have collected are real. Sites that require a phone number with no explanation are the ones losing submissions. The check takes about ten minutes.
Three of those four take two minutes. The fourth is the one almost nobody runs, and it is the one that settles the argument internally.
Check it yourself
- Open your main form on a phone, not a desktop. Count every input a user must complete.
- Is the phone field marked required? Is there any sentence near it explaining what the number is for?
- Tap the phone field. Does a number pad appear, or a full QWERTY keyboard? A letter keyboard means the input type is wrong.
- Export your last 1,000 form submissions. Count how many phone numbers have fewer than 7 digits or follow an obvious pattern like 1234567 or 5555555. That percentage is your fake rate.
That last step is borrowed from GitLab, who ran exactly this analysis on their own trial signup form. If you would rather not go through your form field by field, Revslip runs the same checks on your URL and ranks what it finds by what it is costing you.
Why does a phone number field cost conversions?
A phone number is the one piece of contact information users associate with an unwanted sales call. Baymard Institute's usability testing found that when a phone field is required without explanation, users either abandon or enter a false number. The friction is not the typing. It is the inference about what happens next.
This is a specific mechanism, not general friction. Steve Krug's argument in Don't Make Me Think is that users do not read pages, they scan them and make snap judgements. A required phone field is a snap judgement waiting to happen, and the judgement is usually "they are going to call me."
Which produces the second cost, and the one that gets missed. A fake number is not a neutral outcome. In checkout, it breaks card validation and can cause the abandonment you were trying to avoid. In lead gen, it fills your CRM with numbers your sales team burns hours dialling.
An unexplained phone field charges you twice. You lose the people who leave, and the numbers you keep are mostly wrong.
What does the research show?
Zuko Analytics measured field abandonment across 1,362 forms over 12 months. The phone field showed a mean abandon rate of 6.28% and a median of 3.29%. Email was 6.41% mean. Password was worst at 10.50%. The gap between phone's mean and median is the finding: most phone fields are fine, and a long tail of bad ones drags the average up.
Here is the full field comparison from that dataset. The phone field appeared in 1,028 of the forms sampled.
Source: Zuko Analytics field benchmarking, 1,362 forms across 12 months, unweighted means.
In every row the standard deviation exceeds the mean, and every median sits well below its mean. Zuko's own reading is that most forms handle these fields acceptably, with a tail of badly implemented ones pulling the average. So the phone field is not inherently toxic. A badly built phone field is.
What "badly built" costs is well documented. In a 2017 test run by NextAfter for the nonprofit Care Net, adding a phone field to a course signup form dropped conversion from 99.6% to 62.9%, a relative decline of 36.9% at 100% confidence across 1,454 visitors. The field was optional. Its presence alone did the damage.
And the data you gain is often worthless. GitLab, analysing the most recent 1,000 submissions to their SaaS trial form, found 77.8% of submitted phone numbers were fake, counting anything under 7 digits or following an obvious keypad pattern. That number is published openly in their issue tracker.
One statistic we cut
The most-repeated figure in this topic is that requiring a phone number reduces form submissions by up to 37%, attributed to HubSpot. Revslip could not trace it to any published HubSpot study. The chain ends at blog posts citing other blog posts. Treat it as unsupported until someone produces the original.
Your site
This is one signal. Revslip checks about 200 and tells you which are costing you money.
What do people say about phone number fields?
In Baymard Institute's checkout usability testing, participants consistently described the same reasoning: they cannot see why the number is needed, they assume it will be used for marketing, and they have developed habits for getting past the field without giving a real answer.
"Normally I wouldn't fill in something like 'Phone Number'…I simply can't see what they need that for."
Baymard Institute checkout testing participant"I don't want to be called by some sales dude. That happens sometimes and…it turns me off completely. But now I've learned to type '9999'."
Baymard Institute checkout testing participant"'In case there's a billing issue', let me see…'Don't worry, we never share a number with anyone'. This is helpful."
Baymard Institute participant, on a form that explained itselfThe third quote is the one to notice. The same user who resists an unexplained field accepts an explained one. Baymard's conclusion is that a short inline explanation alleviates the vast majority of privacy concerns. Yet 39% of sites in their ecommerce benchmark still require a phone number with no explanation at all.
How do you fix the phone number field?
Work in this order: prove whether the data is used, remove the field if it is not, make it optional if removal is contested, add an inline explanation if it must stay required, and fix the input type and formatting rules. Most sites can complete all five steps in an afternoon.
- Run the fake-number audit first. Export the last 1,000 submissions and count numbers under 7 digits or with obvious patterns. This gives you a percentage, and a percentage ends arguments that opinions cannot. Check: you have a single number you can put in an email.
- Ask whether anyone dialled. Pull the last 90 days and find out how many of those numbers were called. If the answer is zero, the field is collecting nothing at a cost. Check: you can name the person who uses this data, or you cannot.
- Remove the field, or make it explicitly optional. Removal performs better. Optional is the realistic first move when someone in sales will fight you. Mark it clearly, because an unmarked field is treated as required. Check: load the form fresh and confirm you can submit without it.
- If it stays required, explain it inline. One short sentence next to the field, not in a tooltip on mobile. "In case there's a problem with your order" is enough. Say what you will not do with it too. Check: the explanation is visible without tapping anything.
- Fix the input type and stop enforcing a format. Use
type="tel"so mobile shows a number pad. Accept spaces, dashes and country codes, then normalise on the back end. Baymard found 89% of test participants entered their number in a format different from the one requested. Check: on a phone, tapping the field shows digits, and a number with spaces submits without an error.
How do you know it worked?
Track form completion rate as the primary metric and fake-number percentage as the secondary. Compare two full weeks after the change against the two weeks before, matching days of the week. On a form receiving under roughly 400 submissions a fortnight, expect the result to be directional rather than statistically conclusive.
Two honest cautions about measurement.
First, most small sites will never reach statistical significance on a single field change. If you get 60 submissions a month, a 10% improvement is invisible inside normal variance. That does not mean the change was wrong. It means your evidence is the mechanism and the fake-number rate, not your own A/B test. Removing a field that 77.8% of people lie in does not require a test to justify.
Second, watch lead quality, not only lead count. If you remove the phone field and volume rises 15% while qualified leads stay flat, you have made your sales team's week worse. Track both, and give it a full sales cycle before concluding.
When should you keep the phone number field?
Keep a required phone field when a human calls every lead quickly and deal size justifies the lost volume. In high-ticket B2B, filtering for people willing to be called is a feature rather than a cost. The field earns its place when the call is fast, expected, and worth more than the submissions it deters.
Concretely, keep it if all three are true: someone contacts leads by phone within one business day, average contract value is high enough that fewer better leads beats more weaker ones, and you explain the call at the point of the ask. Miss any one of those and you are paying the friction without collecting the benefit.
There is also a legitimate ecommerce case. Couriers use phone numbers for delivery, and card issuers use them for validation. That is exactly why the explanation matters more than the field. Baymard's finding is not "never ask." It is "never ask silently."
One more limit worth stating. The Zuko dataset measures field-level abandonment, not revenue, and it does not segment by whether the field was required or explained. It tells you the phone field is not uniquely toxic. It cannot tell you what your phone field is doing. Only your own numbers can, which is what the check at the top is for.
Common questions
Does making the phone field optional work as well as removing it?
Usually not quite. In the NextAfter test at Care Net, an optional phone field still reduced conversion by 36.9%, because the field's presence alone signalled a future call. Removal outperforms optional. Optional is still a reasonable first step when removal is blocked internally.
How many people refuse to give a phone number at all?
In Baymard Institute's quantitative study of 1,026 online shoppers, 14% said they would never give an online store their phone number. For comparison, 27% said the same about date of birth and 14% about gender.
What should the explanation next to a phone field say?
One short sentence naming the specific use, placed inline beside the field. "Used for payment validation" or "In case there's a question about delivery" both tested well in Baymard's research. Adding what you will not do with it, such as not sharing it, helps further.
Why do users enter fake phone numbers instead of leaving?
Because leaving costs them the thing they came for. GitLab found 77.8% of phone numbers on their trial form were fake. Users who want the product but not the call take the third option, which means a required field can look like it is working while collecting almost nothing usable.
If you want the rest of the picture, the conversion leak index covers every signal we check, how many form fields is too many deals with length rather than any single field, and the 20-minute traffic diagnostic is the place to start if your form is not the only thing you suspect. Revslip's audit checks run these tests automatically and price each finding, using the published leak formula.
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