On WhatsApp Business you can reply automatically to every customer who writes to you, within 24 hours of their last message. After that window you can only send a pre-approved message template, and templates are paid. That is where automation stops: a customer you don't answer inside the window has to be reached some other way.
Most businesses find WhatsApp as the channel where customers ask quickly, briefly and in the evening. A message arrives late in the afternoon, "do you have a free slot tomorrow?", you're already out, you reply the next day. In the meantime the customer has asked two other providers. An automatic reply fixes that problem. It doesn't fix all of it.
How does the 24-hour window on WhatsApp work?
According to Meta's pricing documentation for the WhatsApp Business Platform, a user's message opens a 24-hour customer service window. Inside the window a business can send free-form messages. Outside it, only message templates can be sent, and those are paid.
Each new customer message renews the window. What matters is who starts: if the customer writes, you're inside the window. If you want to start, there is no window.
| Situation | What you can send |
|---|---|
| The customer wrote to you less than 24 hours ago | A free-form message, automated if you like |
| The customer wrote more than 24 hours ago | Only an approved message template (paid) |
| The customer has never written to you | Only an approved template, and only if they agreed to that kind of messaging |
Exact prices and template categories change, so check them in Meta's documentation rather than in this post.
What can you automate inside the window?
Inside the window the limits are fairly wide. The sensible use is the repeat questions where the answer is always the same or can be read from your calendar:
- Opening hours, address, parking. The answer never changes.
- Free slots. The agent reads the calendar and offers two times.
- Collecting details. Name, phone number, what the customer needs, by when.
- Quote enquiries. The conversation ends with the details collected, which then go into a quote.
- Handover to a person. Anything unclear goes to you, with the whole conversation so far.
More on writing the first reply is in How to write a good first reply to an enquiry. A similar 24-hour limit applies on Instagram, covered in Instagram bookings for salons.
Where does WhatsApp automation stop?
Three limits businesses most often overlook:
- Time. If the customer doesn't reply after 24 hours, you're left with a paid template. So the first reply is the one that counts.
- Consent. A template is not a shortcut to a customer who never wrote to you. The GDPR in Article 4(11) defines consent as "any freely given, specific, informed and unambiguous indication of the data subject's wishes", and Recital 32 says silence, pre-ticked boxes or inactivity do not constitute consent.
- Telling people it's an AI. Article 50(1) of the EU AI Act (2024/1689) requires that people interacting directly with an AI system are informed of it, unless that is obvious. Under Article 113, Article 50 applies from 2 August 2026. So the first message should say plainly that an assistant is replying, not a person.
This isn't legal advice. If you automate anything involving personal data, sign a data processing agreement with every provider and check where the data is processed.
Auto-reply, rule-based bot or AI agent: which one?
| Greeting message | Keyword rules | AI agent | |
|---|---|---|---|
| What it does | Sends the same message to everyone | Replies when a given word appears | Understands the question and answers in your tone |
| Fits | Opening hours, "we'll reply within an hour" | A narrow set of questions | Varied questions, collecting details |
| Weakness | Doesn't answer the question | Breaks if the customer words it differently | Needs clear rules and a handover to a person |
For many small businesses a very good greeting and a clear next step is enough. An AI agent pays off when questions arrive often and look alike.
How to start today
- Go through your last 20 WhatsApp conversations and mark the questions that repeat.
- Measure how long it takes from a customer's message to your reply.
- Write answers to the five most common questions, the way you'd write them yourself.
- Decide when a person takes over, and who.
- Check in Meta's documentation how your chosen connection method handles the window and templates.
How reply speed affects winning a customer is covered in Speed to lead: what the research says. An overview of what can be automated is on the homepage, and for a conversation about your case, get in touch.
Frequently asked questions
Can WhatsApp Business reply automatically?
Yes. When a customer writes to you, a 24-hour customer service window opens, and inside it you can send free-form messages, including automated ones. After the window closes you can only send a pre-approved message template, which is paid.
Can I message customers on WhatsApp who haven't written to me?
Only through an approved message template, and only if the customer agreed to that kind of messaging. Under the GDPR consent must be freely given, specific, informed and unambiguous. Silence or a pre-ticked box is not consent.
Do I have to tell customers that an AI is replying?
As a rule, yes. Article 50(1) of the EU AI Act requires that people interacting directly with an AI system are informed of it, unless that is obvious. Article 50 applies from 2 August 2026. This isn't legal advice.
Sources
Luka Tomič · Founder of Alra
Luka builds AI systems for Slovenian businesses that want to get more done with the same team. He writes about what he sees with clients: where time gets lost and how to get it back.