WhatsApp Flows API: forms inside the conversation

A WhatsApp Flow is a form that opens inside the conversation: several screens, fields and choices, without leaving WhatsApp. Nodium manages its life cycle at Meta through a REST API (create, version, preview, publish, send) and delivers each answer to your webhook.

Updated November 10, 2026Read as Markdown

What you can do

POST /flows creates a draft at Meta; without JSON of your own it starts from a four-screen quote request.
POST /flows/{id}/versions saves a new version, which Meta validates: validationErrors says what to fix.
GET /flows/{id}/preview returns the page Meta renders: the form as on a phone.
POST /flows/{id}/publish is final: a published Flow can no longer be changed. To change it, duplicate it.
A dynamic Flow calls your own endpoint between screens: Nodium decrypts Meta's call, relays it to your HTTPS address and encrypts your answer.

Send a Flow

Shell

curl https://nodium.io/api/v1/messages \  -H "Authorization: Bearer $NODIUM_KEY" \  -H "Content-Type: application/json" \  -d '{    "channelId": "<channel id>",    "to": "+33612345678",    "type": "interactive",    "form": { "kind": "flow", "flowId": "<meta flow id>", "buttonLabel": "Book a slot" },    "idempotencyKey": "booking-1042-form"  }'

An interactive Flow message goes out inside the 24-hour window. To open a Flow for someone who has not written, or in a broadcast, put it on a button of an approved template.

Read the answers

A completed form arrives as message.received with data.reply.kind set to flow, the fields the person filled, and your own flowToken when you sent one.

Frequently asked questions

Can I change a published Flow?

No, this is Meta's rule: a published Flow is final. Duplicate it into a new draft, change the draft, publish it, and deprecate the old one.

Does a Flow need my own server?

Not always. A static Flow carries everything in its JSON. A dynamic Flow, which fetches data between screens, calls an HTTPS endpoint of yours through Nodium.