The one optional field that doubled our reply rate

I'm going to tell you the field in the second paragraph because burying it would be cheap.

The field is a single optional line, placed above the message box, that says: "What's the best way to reach you?"

The input is a plain text box. No dropdown, no toggle, no list of channels to pick from. Just a text field where the user writes whatever they write. Most people write their email (which we already have). A significant chunk write something else — a phone number, a Calendly link, "WhatsApp is faster," "Slack @ mycompany," "after 6 pm Lisbon time please." A few write things like "honestly just reply to this, my Gmail is fine."

That was it. One optional field. Nothing about our product changed. Nothing about our notification pipeline changed. Our reply-to-reply rate — the percentage of contact form submissions where the person wrote back after we replied — went from 41% to 84% over eight weeks.

Here's what I think happened.

The numbers

We ran this by accident, not as an A/B test. We added the field because one customer's feedback in a support ticket asked for it. A month in I noticed our dashboard looked weird. Our "reply received" column had way more green in it. I pulled the numbers.

Period	Submissions	We replied	They replied back
Before the field (6 weeks)	214	211 (99%)	88 (41%)
After the field (8 weeks)	262	259 (99%)	218 (84%)

The reply rate on our side barely moved (we already replied to basically everything). The reply-back rate doubled. That's 130 more conversations in eight weeks than we would have had otherwise. For a small team, that's a sales quarter's worth of extra contact.

I was suspicious of my own data. I waited another four weeks and the pattern held. 82%. Then I removed the field for a week as a sanity check. Reply-back rate dropped to 47%. Put the field back. Back to 81%.

It's the field.

Why I think it works

I have a few theories and they probably all contribute.

The field lowers the perceived cost of writing back. When someone tells you up front that Slack is faster, or that they prefer afternoons, or that their email is a mess and they'd rather WhatsApp — they've told you exactly how to maximize the chance of a productive reply. You're no longer sending a cold email to a stranger hoping it cuts through. You're using the channel they named.

It signals that a human will reply. The presence of the field is itself a message. You're asking me how to reach me, which means you plan to reach me, which means this isn't a black hole. We underestimate how much users expect contact forms to be one-way, and how much they adjust their effort up when they believe someone will read what they wrote.

It captures context we'd normally miss. A surprising number of people wrote things like "I'm in a different timezone, so mornings are best" or "I can't answer calls at work but email is fine." Without the field, we'd have guessed wrong on replies from a quarter of submitters. With the field, we match their rhythm, and they reply back because our reply arrived at a moment they could engage with it.

It's optional. This matters more than I expected. We made it required for one week and reply-back rate was still up, but submission rate dropped by 9% (people abandoning rather than filling it in). Optional kept the conversion on the form itself intact and unlocked the secondary benefit. Required would have cost us more than it gave us. Optional is the right shape for this kind of field.

What people actually wrote in the field

A rough breakdown from the first ~250 submissions:

What they wrote	Share
Their email (the one we already had)	48%
A phone number	14%
A note about timing ("afternoons best")	12%
A different email or forwarding address	9%
A chat handle (Slack, Telegram, WhatsApp, Discord)	7%
A calendar link	4%
"Honestly, just reply here" or similar	3%
Nothing / blank (left it optional)	3%

Notice that 48% wrote back the same email we already had. At first I assumed those were wasted. They weren't. Even when the information wasn't new, the act of answering the question seemed to change how engaged the user was with the outcome. They weren't passively submitting a form anymore. They were telling us how to reach them — a tiny, voluntary action that created commitment.

The rule I've taken away

If you want more replies to your replies, give users one extra opportunity to tell you how they want to be reached — and make it optional.

I am not a fan of extra fields in general. I've written two posts about why contact forms should be short. This is the exception because the field's job is not to collect information. Its job is to start a conversation in the user's head about how they'll respond. The information is a bonus.

If "what's the best way to reach you?" feels too on-the-nose for your brand, here are variants that carry the same psychological load:

• "Anything we should know about how to reach you?"
• "Prefer email, phone, or something else?"
• "Best way / time to reply?"
• "How do you usually like to be contacted?"

Pick one. Add it above your message box. Make it optional. See what happens.

The part I still don't fully understand

I cannot explain cleanly why this field outperformed every other tweak I've made to the contact page combined. I ran bigger changes — new headlines, new layouts, new button text — and none of them moved the reply-back rate the way this one did. The button test from the other post improved form completion; this field improved what happened after the form.

They live on different axes. I'm going to keep exploring whether there's a pattern to "field improvements that reshape the downstream conversation" vs "copy improvements that just get people to click." If I find something worth saying, I'll write it up.

Until then: the field is the field. Add it today. Come tell me what happens.

---

All of this is easier when the form backend you use lets you add optional fields without a schema migration, see the submissions in a dashboard you can actually read, and reply through whatever channel makes sense. FormTo's free plan is enough to run your own version of this experiment on your own contact form.

Adjacent reading: the button A/B test and what 10,000 submissions taught us about how people write.