Coexistence: keep your WhatsApp Business App while using the API

WhatsApp coexistence is Meta's feature that lets you use the WhatsApp Business App and API together on the same number. The app keeps working on your phone. At the same time, a platform like Relay runs that number through the Cloud API, so your team gets a shared inbox, campaigns and automations. Your chats stay in sync both ways.

TL;DR

• Coexistence keeps your existing number live on the WhatsApp Business App. You don't delete the app, change your number or tell customers anything new.
• Your team sees every message. Up to 6 months of past one-to-one chats can be imported, and replies typed on the phone show up in Relay's inbox too.
• Two different time limits: the history covers up to 6 months of past chats, and it has to finish syncing within 24 hours of linking.
• Meta caps coexistence numbers at 20 messages per second. Relay paces sends on these numbers to match, and that pacing applies only to coexistence numbers.
• One rule protects your phone: a coexistence number is never re-registered for the API.

What is WhatsApp coexistence?#

WhatsApp coexistence is a way to connect a number that is already on the WhatsApp Business App to the WhatsApp Cloud API without taking it off the phone. Meta's developer docs call this "onboarding WhatsApp Business app users". Once it's set up, the business can send high volumes through a platform while still chatting one-to-one in the app. In Meta's words, "WhatsApp keeps messaging history between both apps in sync" (Meta for Developers, checked 28 September 2026).

Before coexistence, you had to choose. The number lived either on the phone app or on the API, and moving it to the API meant deleting it from the app first. If the number on your shop signboard, clinic prescription pad or coaching-centre pamphlet was already on the WhatsApp Business App, a proper team setup meant giving up the phone or switching to a new number. For a full breakdown of what each side can and can't do, see WhatsApp Business App vs API.

Coexistence takes away that choice. The owner of a real estate agency can keep answering walk-in leads from their phone while two sales executives work the same conversations from a shared inbox.

How do you use the WhatsApp Business App and API together on one number?#

Two things happen when a number is linked through coexistence:

1. Meta links the number to your API account without re-registering it. A normal Cloud API setup includes a "registration" step for the phone number. Meta's coexistence guide tells platforms to "skip the phone number registration step, as the number is already registered" (Meta for Developers, checked 28 September 2026).
2. Your WhatsApp Business Account is connected to Relay. This is the only wiring coexistence needs, and it is how incoming messages reach Relay's inbox.

Because nothing needs registering, there is no PIN. A standard API connection asks for the number's two-step verification PIN to finish registration. A coexistence connection asks for none, and Relay's connection status panel deliberately shows no "finish registration" step for it. That missing step is the correct state, not a fault (Relay docs: WhatsApp numbers).

What syncs between the WhatsApp Business App and Relay?#

Put simply, your team sees every message, whichever side it came from.

• Past chats. When the number links, Meta can send across your existing one-to-one conversation history. Relay imports it so the shared inbox isn't empty on day one. You choose whether to share that history. Meta's flow asks you to confirm it in the WhatsApp Business App during signup.
• Replies typed on the phone. When the owner answers a customer from the WhatsApp Business App, the reply shows up in the same Relay conversation. Nobody on the team ends up answering a customer who has already been answered.
• Contact names. Names from the phone's contact book are applied to contacts you already have conversations with, so your inbox shows "Dr. Mehta's clinic" instead of a bare phone number. Relay does not import the rest of the phone book, such as family and friends.

Some practical details:

• Replying from the phone pauses Relay's AI auto-reply on that conversation. A human has taken over, so the bot steps back and leaves a note in the thread. If you're setting up a bot, see how to build a no-code WhatsApp chatbot with AI replies and the AI assistant docs.
• Imported history doesn't trigger anything. Old messages don't fire automations, chatbot flows, AI replies or outbound webhooks. They also don't count toward your plan's message usage. The same goes for replies you type on the phone.
• Group chats stay on the phone. The Cloud API doesn't support groups, so they never appear in Relay.

How much chat history does coexistence import, and how long does the sync take?#

These are two separate numbers, and they are easy to mix up:

Source for both: Meta for Developers, onboarding WhatsApp Business app users, checked 28 September 2026.

So there is no "6-month sync window". Meta sends up to six months of chats, and all of it must arrive within the first day. Meta says that if the sync doesn't finish within 24 hours, the business "must be offboarded" and has to go through the flow again. It also allows the history sync and the contacts sync to run only once per link.

Three things help it go smoothly:

• Keep the WhatsApp Business App open on the phone while the sync runs. Meta specifically advises this.
• Keep using Relay. The import runs in the background.
• Don't disconnect and reconnect to "speed it up". Reconnecting restarts the 24-hour window, and anything that wasn't imported stays only on the phone (Relay docs: WhatsApp numbers).

What stops working in the WhatsApp Business App after linking?#

Most of the app keeps working as it did. Per Meta's feature table (checked 28 September 2026):

• Turned off in the app for one-to-one chats: disappearing messages, view-once photos and videos, and live location.
• Broadcast lists are disabled. You can't create new ones, and existing lists become read-only. This matters for D2C brands and travel agencies that send offers from the phone. Once linked, those sends should move to Relay's campaigns, which use approved templates.
• Still in the app but not available through the API: voice and video calls, the catalog, orders, status, labels, quick replies, greeting and away messages, and group chats.
• Linked devices: Meta unlinks companion devices during onboarding. Supported ones can be linked again afterwards. WhatsApp for Windows and WhatsApp for WearOS are not supported with coexistence.

Meta also lists a primary phone that has been inactive for about 14 days as one reason a number gets disconnected from the API (same source, checked 28 September 2026). Keep the phone in regular use.

Why are coexistence numbers limited to 20 messages per second?#

Meta's documentation states that "business phone numbers that are in use with both the WhatsApp Business app and Cloud API have a fixed throughput of 20 mps", meaning 20 messages per second (Meta for Developers, checked 28 September 2026). The phone and the API share one number, so they share its sending capacity.

Relay paces sends on each coexistence number so they stay within that ceiling. This is a deliberate safety choice. If a platform sends faster than a coexistence number allows, the extra messages come back as rate-limit errors, which means customers on your campaign list who never receive the message. Pacing keeps sends within the limit so they aren't rejected for going over it.

Two points to keep in perspective:

• 20 messages per second is 1,200 per minute (20 × 60). A 5,000-contact campaign for a coaching institute's admission reminder finishes in about 4 minutes and 10 seconds at that rate (5,000 ÷ 20 = 250 seconds). For most small businesses the cap is invisible.
• This pacing applies only to coexistence numbers. A number connected only to the API is not held to 20 messages per second by Relay, and pacing on one number never slows down your other numbers.

Is my number eligible for WhatsApp coexistence?#

Based on Meta's documentation (checked 28 September 2026), a number is a candidate if:

• It is already active on the WhatsApp Business App. Coexistence is for numbers already on the Business App, not the regular WhatsApp app and not a number that's already on the API.
• The app is up to date. Meta requires WhatsApp Business App version 2.24.17 or later (Meta for Developers).
• The phone stays in use. See the 14-day inactivity point above.

Meta's current coexistence guide doesn't publish a list of excluded countries, so we won't claim one here. The reliable test is Meta's own signup flow, which checks each number when you link it.

How do you set up coexistence with Relay?#

In Relay, coexistence onboarding is available on request, during onboarding with our team. It isn't a self-serve switch today. Our team turns it on for your account and helps you through Meta's signup.

Here's what to expect:

1. Our team turns on the "I already use the WhatsApp Business app" option for your account. It sits next to the standard Meta signup under Settings → WhatsApp (Relay docs: connect WhatsApp).
2. You go through Meta's own signup flow. You enter your WhatsApp Business App number, confirm the connection from the WhatsApp Business App on your phone, and choose whether to share your chat history. No PIN is needed, because there is nothing to register.
3. The history import starts. Keep the app open on the phone while it runs.
4. Your status panel shows the connection as Coexistence, with no "finish registration" step. That's expected.

If you ever want to unlink, disconnecting a coexistence number in Relay removes Relay's access, and the number keeps working on the WhatsApp Business App. Your contacts, conversations and messages in Relay are kept (Relay docs: WhatsApp numbers). Remember that reconnecting later restarts the 24-hour history window. Meta also lets the business disconnect from the app itself, under Settings → Account → Business Platform.

Does coexistence cost extra?#

Coexistence isn't a separate Relay plan or add-on. It's one way to connect a number, and it counts as one connected number like any other. Messages sent through the API on a coexistence number are billed from your prepaid wallet at Relay's standard per-message rates, the same as any other connected number. From 1 October 2026, Relay's wallet rates for messages to Indian numbers are ₹1.05 per marketing message and ₹0.17 per utility, authentication or service message, GST included.

On Meta's side, messages typed in the WhatsApp Business App "will continue to be free", while messages sent through the Cloud API are billed at Cloud API rates (Meta for Developers, checked 28 September 2026). Messages you send from the app also don't open or extend API messaging windows. One detail to know: the API's customer service window only opens for messages received after onboarding. If a customer wrote to you just before you linked, a reply sent through the API has to be a template. For India rates, see our guide to WhatsApp Business API pricing in India.

Should you choose coexistence or a dedicated API number?#

Choose coexistence if a real phone is currently the main way your business answers this number, and you want to keep it that way. For example, a clinic whose receptionist replies from the counter phone, a travel agency owner who closes bookings from their own handset, or a real estate broker whose number is printed on every hoarding.

Choose a dedicated API number (standard Meta signup) if the number is new or will be used only through Relay. You get throughput that isn't shared with a phone, all API features, and no phone to keep active.

Either way, Relay, the WhatsApp Business platform for Indian SMBs, gives your team the same shared inbox, campaigns, chatbots and AI replies on top.