Write the broadcast message

Each number sends one approved template, with its blanks filled from the contact or from a fallback you choose.

Quick start

In the broadcast, scroll to Message Content. A channel must be chosen first.
Click Add Content (or a number's tab), then choose an approved Template — what this number's recipients will receive.
For each blank pick a Source: Contact field, Same text for everyone or Tracked link.
A Contact field also needs a Fallback. Fill any Header link and button value.
Read the preview, then go on to Review. Nothing is sent here.

You cannot write free text. A broadcast always sends an approved template.
A fallback is required on every blank filled from a contact detail, and it cannot be empty.

Details

Broadcasts → open the broadcast → the Message Content section, under Configuration.

A channel has to be chosen first. Clicking Add Content without one outlines the Channel field instead.
The template must already be approved on that number. Templates are synced under Settings → Templates.
With Last interacted channel, every ticked number gets its own tab and its own template.

Field	What it means	Default	Limits
Template	The approved template to send, shown as its name and language.	—	—
Header variable	The blank in a text header.	—	—
Image / Video / Document URL	The web address of the picture, video or file a media header carries.	—	—
Body variables	One row per blank in the message body, numbered the way the template numbers them.	—	—
Contact field	Fill the blank from that person's Full name, First name, Phone or Email.	—	—
Same text for everyone	One fixed piece of text.	—	—
Tracked link	A link each person gets their own copy of, so clicks can be counted.	—	—
Fallback	What to use when that contact's field is empty.	there	Required, and it cannot be blank: WhatsApp refuses an empty value.
Buttons	A quick-reply value, a copy code, or the ending of a link, depending on what the template's buttons are.	—	Only buttons that need a value from you appear.

Template: The approved template to send, shown as its name and language.
Header variable: The blank in a text header.
Image / Video / Document URL: The web address of the picture, video or file a media header carries.
Body variables: One row per blank in the message body, numbered the way the template numbers them.
Contact field: Fill the blank from that person's Full name, First name, Phone or Email.
Same text for everyone: One fixed piece of text.
Tracked link: A link each person gets their own copy of, so clicks can be counted.
Fallback: What to use when that contact's field is empty.; Default: there; Limits: Required, and it cannot be blank: WhatsApp refuses an empty value.
Buttons: A quick-reply value, a copy code, or the ending of a link, depending on what the template's buttons are.; Limits: Only buttons that need a value from you appear.

Choosing a template lays out exactly the blanks that template has. Change the template and the rows are rebuilt to match.
Every body blank starts as First name with the fallback there, so a message reads sensibly before you touch anything.
A fallback is required on any blank filled from a contact detail, and it cannot be empty: WhatsApp refuses an empty value and would take the whole send down with it.
A Tracked link gives each person their own copy of your link. Clicks on it are what the report's Clicked and Click rate count.
Choosing Tracked link renames the box beside it to Link, and that is where the web address goes.
A text header takes the same three sources as a body blank. A picture, video or document header takes a plain web address instead, the same for everybody.
Buttons come from the approved template, and only the ones that need a value from you appear. A quick-reply button takes a value your workflow can read, a copy-code button takes the code, and a link button takes the part of the address that changes per person.
The preview under the rows shows the template with your choices applied.
What this section accepts is exactly what publishing accepts, because both read the template's shape with the same reader.
With Last interacted channel, the tabs across the top are your ticked numbers. A tab with nothing written yet carries a red dot.
Everything saves by itself as you work.

No approved template on that number: No approved templates on this channel — sync them under Settings → Templates.
Publishing before choosing a template: Pick a template for the message.
A template that is not approved: Only approved templates can be broadcast.
A template that belongs to another number: That template belongs to a different channel.
A blank left with an empty fallback: Give a fallback — WhatsApp rejects an empty parameter. The message points at the row it means.
With several numbers, one tab left empty: Every selected channel needs a message.
Add Content clicked before a channel is chosen: the Channel field is outlined and says This field is required.

You cannot write free text here. A broadcast always sends an approved template, because many people on a list are outside the 24-hour window in which WhatsApp allows free text.
You cannot edit the template itself from here, and you cannot add a button the template does not have.
Only four contact details can fill a blank: Full name, First name, Phone and Email. Your own contact fields are not offered.
The preview shows your setup, not a real person's message. It does not prove the number is reachable or the picture loads — a test send does that.
One template per number. Two versions of a message need two broadcasts, or two numbers.
A media header takes a web address, not a file from your computer.

Write the fallback as a real greeting, not a blank. Every contact with no first name reads it.
Send yourself a test before you publish. It is the only way to see what the picture and the buttons actually do.
Use a Tracked link whenever you want to know whether the campaign worked. Without one the report has no click figures.
Keep the same template name across numbers when you use several, so the tabs are easy to check.

A festival greeting with the customer's first name, and a fallback of there.
A back-in-stock message with the same text for everybody and one tracked link to the product.
Two numbers, two brands: one tab each, two templates, one broadcast.
A voucher template with a copy-code button, where you type the code once.

Can I just type my own message?: No. A broadcast always sends an approved template, because many people on a list are outside the 24-hour window in which WhatsApp allows free text.
What happens to somebody with no first name?: They get the fallback you typed. That is why it is required.
Why can I not use one of my own contact fields in a blank?: The picker offers name, first name, phone and email only. Put the value in the template as fixed text, or split the send by segment.
Does the preview mean it will work?: It means your setup is complete. Only a test send proves the picture loads and the buttons behave.
Can I change the message after publishing?: No. Cancel the broadcast back to a draft while it is still scheduled, change it, choose the timing again, and publish.

Reading this with an AI assistant? Plain Markdown version.