How to build your WhatsApp audience

Q: How do I import phone numbers from a CSV?

Go to the Prospects page and choose Import, select your CSV, and on the mapping screen map your phone column to the WhatsApp Phone field along with first_name and last_name. Map any extra columns to custom fields for personalization, then save everyone to a named list. That list is selectable as the audience in any WhatsApp campaign.

WarmySender Team

Updated Aug 26, 2026

You bring the phone numbers. Upload a CSV of numbers in international format (like +14155550123) on the Prospects page and save everyone to a reusable list, or paste numbers straight into the campaign wizard for a quick one-off. There is no WhatsApp number search inside WarmySender, and there won't be — the people you message should be people you genuinely chose.

Can I search for WhatsApp numbers inside WarmySender?

No. WhatsApp has no prospect search of any kind, and WarmySender never scrapes, guesses or harvests phone numbers. Your audience is always the numbers you already have.

That's also the safest possible starting point for your number. WhatsApp restrictions are driven overwhelmingly by whether the people you message wanted to hear from you: a small list of people with a real reason to expect your message will outperform — and outlive — a large list of strangers every time. A number that is blocked or reported by its recipients is the fastest way to lose it.

Nothing in WarmySender checks a number against WhatsApp before you send, either. If a number simply isn't on WhatsApp you'll find out when the first message is attempted, and that person is quietly skipped from then on — no repeated attempts, nothing for you to clean up.

What format do the phone numbers need to be in?

International format, with the country code — for example +14155550123 for a US number or +491712345678 for a German one. That is the one rule that matters.

Beyond that, WarmySender is forgiving about punctuation. All of these are read as the same person:

+1 415 555 0123
(+1) 415-555-0123
0014155550123 — the 00 international prefix works too
14155550123 — bare digits, country code included
a wa.me/14155550123 link

What doesn't work is a national number with no country code, like 07123 456789. WarmySender deliberately refuses to guess which country that belongs to, because guessing wrong means messaging a complete stranger. Add the country code before importing and the number is accepted.

Because everything normalizes to one canonical form, the same person written three different ways across three files stays one person — no duplicates, and nobody gets messaged twice.

How do I import phone numbers from a CSV?

Upload the file on the Prospects page, map your phone column to the WhatsApp phone field, and save everyone to a named list. That list is then selectable as the audience in any WhatsApp campaign.

Go to the Prospects page and choose Import.
Select your CSV. A simple set of columns is first_name, last_name, phone.
On the mapping screen, map your phone column to the WhatsApp Phone field — this is what makes each person reachable on WhatsApp. Map first_name and last_name too.
Map any extra columns (company, city, how you know them) to custom fields, so you can personalize each message with them.
Save everyone to a named list — something like "WhatsApp — event follow-ups" — so you can find and reuse the audience.
Open Campaigns → New campaign → WhatsApp and select that list on the Prospects step.

An example file, header row first:

first_name, last_name, phone
Jane, Doe, +14155550123
Marco, Rossi, +39 340 123 4567
Aisha, Khan, 00447700900123

Personalization is worth the extra columns. WhatsApp is a personal channel, and a message that references something true about the person is the difference between a reply and a block.

Can I just paste numbers into the campaign?

Yes. The Prospects step of the campaign wizard lets you paste phone numbers directly, one per line, and WarmySender turns them into your audience on the spot — no file, no import.

This is the right path for a quick one-off: a handful of people you met at an event, or a short list you were handed this morning. The same format rules apply, and the same normalization means a number you paste today is recognized as the same person if it also appears in a list you import next week. You can also start from a saved list and paste a few extra numbers on top.

For anything you'll want to reuse, filter, or add to later, import it as a list instead — a named list is far easier to work with than a paste you can't get back.

What happens to people without a phone number?

They're simply skipped for the WhatsApp steps of a sequence. Nothing errors, nothing pauses, and the campaign keeps running for everyone who does have a number.

This is by far the most common reason a WhatsApp campaign reaches fewer people than expected. If the numbers look low, check how many people in the list actually carry a phone number — then re-import with the phone column mapped, or paste the missing numbers in, and those people become reachable.

A separate case: someone whose number is perfectly valid but who isn't on WhatsApp at all. You'll find that out at send time, and that person is skipped from then on rather than retried. Neither case costs you anything or interrupts anyone else's sequence.

Can one list serve email, LinkedIn, WhatsApp and Instagram?

Yes. A single list can carry an email address, a LinkedIn profile, a WhatsApp phone number and an Instagram handle for the same person, so one audience powers a coordinated multichannel sequence.

Each channel uses the detail it needs and skips anyone missing it — so a person with an email but no phone number still gets your email steps, and one with both gets both. And when someone replies on any channel, WarmySender stops that person's automated follow-ups on all the others, so nobody gets chased on WhatsApp after they already answered your email.

A word of judgement, though: just because you can add a WhatsApp step for everyone doesn't mean you should. It's the most personal channel on the platform. Use it for the people who plausibly expect to hear from you there, and let email carry the volume.

Common questions about WhatsApp audiences

Can WarmySender find phone numbers for my contacts?

No. WarmySender does not look up, guess or scrape phone numbers for WhatsApp, and there is no WhatsApp number search in the product. You bring the numbers you already have — from your CRM, your event list, your existing customers, or people who gave you their number directly.

What format should the phone numbers be in?

International format including the country code, for example +14155550123. Spaces, dashes, brackets, a leading 00 instead of +, and wa.me links are all fine — WarmySender reads them as the same number. A national number with no country code, like 07123 456789, is rejected on purpose rather than guessed at.

Can I check whether a number is on WhatsApp before I message it?

No, and nothing in WarmySender pretends to. If a number isn't on WhatsApp you find out when the first message is attempted, and that person is skipped from then on instead of being retried. Nothing else in your campaign is affected.

Will importing the same person twice message them twice?

No. Every number is normalized to one canonical form before anything is saved, so the same person written as +1 415-555-0123 in one file and 14155550123 in another stays a single person. Re-importing an overlapping list doesn't create duplicates or duplicate messages.

How big should my WhatsApp list be?

Smaller than you'd build for email. One number can start at most 20 new conversations a day — fewer while it's ramping — so a 200-person list is a couple of weeks of outreach on one number. Build the list around who genuinely belongs on it rather than around a target size; the reply rate you get is also the signal that governs how many new conversations your number is allowed to start.

Where exactly do I map the phone column when importing?

On the mapping screen that appears after you select your file on the Prospects page. Match the column holding your numbers (for example phone) to the WhatsApp Phone field, map first_name and last_name to theirs, and send any remaining columns to custom fields for personalization. Then save everyone to a named list.

Can I reuse a list I already built for email or LinkedIn?

Yes — if those people also have phone numbers on their records. Re-import the same list with the phone column mapped and the numbers are added to the people already there; anyone still without one is simply skipped for the WhatsApp steps.