Guidelines

Hong Kong (HK)

Locale Summary
Locale name	Hong Kong
ISO code The International Organization for Standardization two character representation for the given locale.	HK
Region	Asia
Dialing code The dialing prefix used to establish a call or send an SMS from one locale to the given locale.	+852

Reachability Can Twilio complete calls to numbers in this locale?	Inbound Ability to call numbers. Calls are inbound from PSTN to Twilio numbers.	Outbound Ability to call non-Twilio numbers. Calls are outbound from Twilio to PSTN numbers.
Domestic For calls within the locale	Yes	Yes
International Can in-locale numbers be reached from outside the locale?	Yes	Yes
Toll-Free Can in-locale Toll-Free numbers be reached from within the locale?	Yes	N/A
Outbound restrictions Regulatory and/or Carrier restrictions on outbound calls made from Twilio to non-Twilio numbers in this locale	High volumes of outbound calls (e.g., exceeding 5,000 calls per day from a single entity/campaign) characterized by short average call durations (e.g., under 48 seconds) or repetitive dialer patterns may trigger automated carrier-level network blocking as they are automatically seen as potential spam or robocalls. Outbound calls from Toll Free numbers are not allowed. From March 2023, for outbound calling to Hong Kong destinations from Hong Kong caller IDs, please use Twilio numbers as the caller ID (From number). Making calls using non-Twilio phone numbers via the Verified Caller ID service will no longer be supported in alignment with the measures introduced by the Office of the Communications Authority (OFCA) to strengthen protection against scams.
Outbound requirements Conditions that must be met before outbound calls are allowed from Twilio to non-Twilio numbers in this locale	N/A
Best practices Useful tips for best performance on outbound calls to non-Twilio numbers in this locale	Customers should design outbound calling workflows to avoid repetitive, high-frequency, or short-duration call patterns that mimic automated robocalls or suspicious calling behavior. Customers operating high-frequency calling campaigns to Hong Kong should actively monitor answer rates and call duration metrics. A sudden drop in connection rates often indicates carrier-level filtering due to perceived spam thresholds. Distribute high-volume traffic responsibly across appropriate calling windows and legitimate caller IDs rather than concentrating short call bursts through single originating channels.

Caller ID Can Twilio complete calls to numbers in this locale?	Inbound Inbound call receives originator's Caller-ID. Calls are inbound from PSTN to Twilio numbers.	Outbound Outbound call preserves sent Caller-ID. Calls are outbound from Twilio to PSTN numbers.
Domestic For calls within the locale	+E.164	Local
International Can in-locale numbers be reached from outside the locale?	Anonymous	+E.164 (calling to mobile) Anonymous (calling to local numbers)
Toll-Free Can in-locale Toll-Free numbers be reached from within the locale?	+E.164	N/A

DTMF	Inbound Inbound call receives DTMF from PSTN. Calls are inbound from PSTN to Twilio numbers.	Outbound Outbound call sends DTMF to PSTN. Calls are outbound from Twilio to PSTN numbers.
RFC.2833 format Is RFC.2833 DTMF format supported?	Yes	Yes

Emergency Calling Calls are outbound from Twilio to Emergency (911/933) numbers.	Outbound Ability to make Emergency Calls. Calls are inbound from PSTN to Twilio numbers.
Emergency services Are calls to Emergency Services Numbers in the locale allowed over Twilio?	No

For the benefit of all our customers, these guidelines are provided to help you comply with applicable requirements and to help ensure Twilio's platform remains compliant with global telecommunications ecosystem requirements. These guidelines represent our current understanding of common compliance requirements generally applicable to Twilio and its customers, and do not constitute legal advice. By posting these guidelines, Twilio makes no assurances regarding the legal compliance of your application built using our APIs. You are expected to understand and abide by all compliance obligations applicable to your specific application. You should check these pages regularly for updates as telecommunications ecosystem requirements continue to evolve and change, and the information below may be updated or changed without notice.