Seven events
WhatsApp reply rates beat email by a wide margin. They also fall far short of what the sales pitch suggests, and one choice you make at registration decides which of the two you get. The numbers below come from seven events, and the ones that went wrong are here too.
Here are three moments from a real event: the first message, the follow-up questions, and the helpdesk traffic that makes up most of the volume.
Sena
online
Hi Marie, I see you signed up for FOST New York next week.
I am Sena, the event concierge. What do you want from the two days? I will line up your sessions, the sponsors worth your time, and the people to meet.
A sentence or two is plenty, and a voice note is fine if you are on the move.
09:12
Sena
online
Mostly a payments provider we can actually integrate quickly
09:31
Useful, thank you. Two quick things so I get this right:
Is this a decision for now or for later in the year, and is the blocker integration effort or pricing?
09:31
Now, we want something live before Q4. Integration effort is the blocker, pricing is fine
09:34
Got it. Three exhibitors match that, and two of them have engineers on the stand.
Booth 214: ships a drop-in SDK, 2 week typical integration
09:34
What the organizer keeps
Sena
online
which stage is the AI infra panel on
14:02
Stage 3 (Level 2, past the coffee bar on the right).
Starts 14:20, so you have 18 minutes.
14:02
anything after it worth the time
14:03
Same stage at 15:10 there is a session on cost control at scale, which lines up with the integration problem you mentioned earlier.
14:03
We wrote these conversations to show what our conversations look like. They are not real transcripts, and they show no real attendee.
Yes. Most organizers first try a personal account or the free WhatsApp Business app. A message to the whole registration list from either one gets the number banned, usually in the week of the event. The real setup needs approval from Meta and consent from each attendee. Meta sets the pace, and the software is the easy part.
The channel works. Most organizers who plan it never launch it, because nobody tells them about the approvals until three weeks in.
We are not a neutral guide, because we sell this channel ready to send. Every failure on this page is one of ours, and we already paid for each one so you do not have to.
Every number below comes from a named event, and each one says who it counts.
Reply rate by how hard the organizer promoted it
CPME31. 92% of the attendees who received the message replied. Of everyone who opted in, 65% replied.
FOST Singapore. 38% of the attendees who received the message replied, and 67% opened it.
FOST London 2026. 201 of the 1,135 registrants who received the message replied, three times more than at any earlier edition.
An event where the organizer never mentioned the channel to attendees.
Sources: CPME31, FOST Singapore, FOST London 2026.
Swipe the table to see every column
| Channel | Measured | Where it comes from |
|---|---|---|
| WhatsApp, promoted | 92% of the attendees who received the message replied. Of everyone who opted in, 65% replied. | CPME31 Toulouse. Checkbox on the registration form, and the organizer promoted it on site. |
| WhatsApp, lightly promoted | 38% of the attendees who received the message replied, and 67% opened it | FOST Singapore, a content-led event with light promotion |
| WhatsApp, sent to every registrant | 201 of the 1,135 registrants who received the message replied (17.7%), three times more than at any earlier edition | FOST London 2026, six co-located conferences. The message went to every registrant with a phone number |
| WhatsApp, not promoted | Around 6% engagement | An event where the organizer did not mention Sena at all |
| Event app | 20 to 30% of registered attendees typically use it, and ~40% use a well-run app made only to network | What organizers tell us |
The promoted row and the row with no promotion use the same channel. Only the promotion is different.
At FOST Singapore, two-thirds opened the message and one-third replied. Read is not the same as answered, and at a content-led event your message competes with the programme itself.
At FOST London 2026, a reply also went with attendance. Registrants who replied before the event had an 18.8% no-show rate, against 43.5% for registrants who stayed silent. Read the no-show data.
Ask any vendor in this category for the same table. A percentage with no event name next to it is a best case. The useful question is what reply rate the channel got at an event like yours, and what the organizer did to earn it.
Four of these are ours. Number three, the checkbox, is yours.
01
A personal account or the free Business app gets the number banned, often in your event week. Our number already has Meta approval.
02
Meta rejects messages that read like adverts, and each rewrite costs you another wait. Ours already passed.
03
This one is yours: one checkbox on the form your attendees already fill in. We give you the words. Consent you collect later reaches a fraction of the people.
04
Registration exports are full of phone numbers that never deliver. We find them before the first send.
05
Once the first message lands, attendees write back. A question with no answer is worse than no message. Sena answers in seconds from your programme and your floor plan.
The checkbox matters more than anything else we control, the message and the agent included. At CPME31 the checkbox sat on the form and the organizer talked about it on site. 76% of the participants in its business meeting programme opted in. At FOST Singapore the event was content-led and the push was light, and 17% opted in. The product and the channel were the same, and the reach was four times higher.
We write the words and a plan to promote it. We cannot put it on your form for you. A few minutes of your registration team's time decides most of what you get back.
If you build it yourself, plan for two to three months before your event date. Most of that time you wait for Meta, and Meta gives no dates.
Organizers decide on the channel six weeks out, which feels early. In week four the number still cannot send. By then you can launch anyway and risk a ban in your event week. The other choice is to drop the channel and tell the sponsors you promised it to.
With Sena there is no wait, because Meta already approved our number. From you we need your attendee list, your programme, your sponsor list and the checkbox on your form. Events have gone live with us in under two weeks.
WhatsApp adds no GDPR risk of its own. The risk is a message to someone who never agreed, or a question about their data that you cannot answer.
You need an opt-in at registration, a privacy notice, and a clear way for attendees to stop the messages. We publish the companies that handle attendee data for us. This is not legal advice. For an event with EU attendees, ask a qualified person to check the setup.
Attendees do ask. At CPME31 one wanted to know where their data came from and whether anyone scraped it. Have a real answer ready.
Each of these cost us time on a real event. On your own, each one costs a week to find.
Attendees still reach you, but nothing you send goes out. Every symptom points somewhere else. We lost a week to that, twice.
One small error in a personalised message stops it for every attendee at once. Meta does not tell you why.
The morning after the event, messages that worked all day start to fail. To reach attendees after the event, you needed Meta approval before it ended.
Missing country codes, landlines, numbers with no WhatsApp account and plain typos all fail on the day you send. At CPME31, more than one in five attendees who opted in never got the message. The gap is never zero.
Each rewrite means another wait. Two weeks before the event is not enough time on a new number, and that is when most organizers start.
If you run several events off one number, a move to a new event can cut off the old one. Attendees still send messages and nothing answers. You find out when an attendee asks why nobody replied.
Once WhatsApp is open to them, attendees use it for everything, and mostly for things you did not build it for. At FOST Singapore, 78% of conversations were about where to go: which stage, which room, what is on next. At FOST Paris the channel handled 2,634 attendee questions, each answered in under three seconds.
Volume runs higher than an email inbox and attendees expect an answer in seconds, not hours. A human-staffed desk at a large event needs more people than anyone plans for. Whatever answers has to read from your actual programme, venue map and exhibitor list. An assistant that guesses a room number does more damage than silence.
Attendees also message to say they cannot make it, to ask for an organizer, to report a problem with the venue. Once the channel exists it becomes the event's front door, so plan for it to be one.
Everything above describes a job that we do, and with Sena none of it lands on your team.
Your attendees reliably answer a question on WhatsApp and nowhere else, so it is the cheapest way to learn why they came. Your sponsors pay for what you do with that answer.
Your side is the checkbox and the promotion. Ours is the rest of this page. Pricing starts at 3,000€ per event.
Yes, but a personal account or the free WhatsApp Business app gets the number banned. The real setup needs approval from Meta and consent from each attendee, and Meta sets the pace. Sena runs on a number that already has Meta approval.
After an attendee writes to you, you can reply freely for 24 hours. Outside that time, you can send only messages that Meta approved in advance. That is why messages that worked all through your event start to fail the next morning.
Put the checkbox on the registration form and promote it. Nothing else we measured matters as much. At CPME31 the organizer promoted it on site, and 76% of the participants in its business meeting programme opted in. At a content-led event with light promotion, 17% opted in.
It can be. The responsibility is yours, and Meta does not carry it for you. You need an explicit opt-in at registration and a clear way for attendees to stop the messages. This is not legal advice, so ask a qualified person to check your setup.
It depends on promotion, and the range is wide. At CPME31, 92% of the attendees who received the message replied. Of everyone who opted in, 65% replied. At FOST Singapore, with light promotion, 38% replied and 67% opened it. Where the organizer did not promote it at all, engagement sat near 6%. Be careful with any vendor who quotes one number with no event attached.
For reach, usually yes, because there is nothing to install and the app is already open on the attendee's phone. For agenda, maps and session bookmarks, no. An event app is the right tool there, and WhatsApp does not replace it. The two solve different problems, and most events run both.
Two to three months if you build it yourself, and most of that time you wait for Meta. Meta gives no dates. The common failure: you decide on the channel six weeks out, and in week four the number still cannot send. With Sena there is no wait, and events have gone live in under two weeks.
Either works. Most events use our number, because Meta already approved it, and that removes the longest wait. Your own number works too, but start earlier, because a new number needs Meta approval first.
Volume is higher and the expected reply time much shorter than an email inbox, so the team most organizers plan for falls short. FOST Paris ran 2,634 attendee questions through the channel, each answered in under three seconds. At FOST Singapore, 78% were navigation questions rather than questions about people to meet. Whatever answers has to work from your real programme and floor plan, and that is the job Sena does.
The anonymized sponsor report from a live 1,306-attendee event, in your inbox.
A real, anonymized sponsor report from a live event. No newsletter, no sequence.
Stuck on one of the failures above? Ask us and we will tell you what we did, whether or not you buy anything.