# Opt-out · STOP, HELP, and START keyword handling for SMS

## One incoming word.  A changed sending rule.

Inspect what STOP, START and HELP mean for a supported sender and subscriber.

9:41 ▮▮▮
‹ h Harbor Text message
Today · 9:41 Harbor updates: your order is ready for collection. Reply STOP to opt out.
STOP
You have opted out of messages from this sender.

+ Text message

Sender preference · Maya
STOPSTARTHELP

Suppression recorded

### The next send is refused

Subscriber
Maya · +1 555 123 4567

Sender
Harbor’s business number

Send result
SMSRecipientSuppressed

The supported keyword blocks this sender-and-subscriber pair. Carry the preference across the program the customer asked to stop.

[Explore opt-outs and keywords](/docs/guides/sms/opt-outs-and-keywords)
Interactive illustration with fictional records. No account operation is performed.

[Explore SMS consent & opt-outs →](/docs/guides/sms/opt-outs-and-keywords)

[Two-way SMS Receive customer texts and reply from your application. →](/sms-api/features/two-way)

[Webhooks React to incoming texts and delivery changes. →](/docs/guides/sms/events)

[Global delivery Understand destination support before sending. →](/docs/guides/sms/overview)

[Explore SMS →](/sms-api)

## Scale without  losing control.

Organize teams in workspaces, control API access, and trace changes through audit logs.

Harbor Organization
Workspaces Production Sandbox

### Delivery agent

API key · Customer operations team
Active
Permissions Access
Email Read & write
SMS Read & write
WhatsApp Read Read & write
AL Alex Lee Admin  Permissions updated

### Audit log

Production
 API key updated Alex Lee · 09:42:18 UTC

Workspace
Production

Resource
Delivery agent

WhatsApp
Read Read & write

Succeeded

 [Workspaces](/docs/guides/workspaces)[Team roles](/docs/guides/users-teams-roles)[API authentication](/docs/guides/authentication)
[Explore Enterprise](/enterprise)

## Start with SMS. Build across channels with Bird.

[Get started](/dashboard/signup?returnTo=%2Fdashboard%2Fw%2Fsms%2Fonboarding) · [Contact Sales](/demo?product=sms)

[Email](/email-api) · [SMS](/sms-api) · [WhatsApp](/whatsapp-api) · [Apple Messages](/apple-messages-api) · [Voice](/voice-api)



## Related resources

- [How do I collect SMS opt-ins?](/explained/sms/how-do-i-collect-sms-opt-ins) (answer)
- [Operate messaging reliably](/learn/paths/reliability) (course)
- [SMS compliance](/sms-api/features/compliance) (product)

[Get an implementation brief](/learn/workspace?topic=consent)