HSM (Highly Structured Message)

HSM (Highly Structured Message) is the message template pre-approved by Meta, mandatory to start a conversation via WhatsApp Business API outside the 24h window. Without an approved HSM, the company is unable to send the first active message to the customer.

Why HSM exists

The Meta rule: the customer is the one who decides when a conversation starts. When the customer sends the first message, a 24-hour "service window" opens in which the company responds freely. Outside of this window, any message from the company must be an approved HSM.

HSM Categories

• Marketing — promotions, offers. It costs more. Restricted in some countries.
• Utility — confirmations, order updates, reminders. It costs less.
• Authentication — verification codes, 2FA. Restricted use case.
• Service — service initiated by the customer. Does not use HSM (within the 24h window).

The approval process

1. Company writes the template on the dashboard BSP.
2. BSP submits to Meta.
3. Approval takes between 1 minute and 48 hours (varies by BSP and Meta load).
4. Once approved, the template receives a unique ID and can be triggered.
5. Rejected templates can be adjusted and re-submitted.

What causes template to be rejected

• Promotional content in a template marked as Utility.
• Generic language that could be interpreted as spam.
• Exaggerated promises or offers that are not fulfilled.
• Lack of placeholder for variable (fixed template).

HSM does not exist without API

If you don't use the official API (you use WhatsApp Web or extension), you don't need HSM. The 24h window is an API-specific limitation; on WhatsApp Web you can start a conversation with whoever you want, as long as you respect spam policies and have consent.

See: Official API, opt-in.