Instance discovery
Home Assistant advertises itself on the local network as the _home-assistant._tcp.local. mDNS/Zeroconf service. Clients (for example the companion apps) can browse for this service to discover instances without asking the user for an address.
The service is registered once the frontend integration has been set up (or on start), so that the HTTP server is up and reachable when the record is published.
Service record
| Field | Value |
|---|---|
| Service type | _home-assistant._tcp.local. |
| Instance name | <location_name>.<service type>. The location_name has . replaced with a space and is truncated to fit the 63-byte DNS label limit. On a name collision, Zeroconf appends a suffix (allow_name_change). |
| Host (server) | <uuid>.local., where <uuid> is the instance ID. |
| Port | The HTTP server port (8123 by default). |
TXT properties
| Property | Meaning | Default |
|---|---|---|
location_name | Friendly instance name, from hass.config.location_name. | Home if no name is configured |
uuid | The instance ID (core.uuid); a stable, opaque 32-character hex identifier. Also reused as the host name (<uuid>.local.). | Generated on first run |
version | Home Assistant Core version. Optional: Clients should treat optional as version currently not known. It typically means Core is not yet installed (for example, landing page shown during initial setup). Currently the landing page advertises with the sentinel version 0000.0.0. This is not a valid Home Assistant Core version, but is merely used to work around limitations of the current Android app. | Current Core version |
internal_url | Internal/LAN URL, resolved via get_url(..., allow_external=False). | "" if unavailable |
external_url | External URL, resolved via get_url(..., allow_internal=False). | "" if unavailable |
base_url | Deprecated; kept for backward compatibility. Set to external_url, or internal_url if there is no external URL. | "" if neither is available |
requires_api_password | Legacy flag, always advertised as True. The api_password authentication mechanism it referred to was deprecated in 0.90 and removed in 2024.7.0, so the flag is now meaningless. Clients should no longer parse it. | True |
landingpage | Present and set to True only on the record published by the landing page before Core is set up. Absent on a running Core instance. | Not set |
note
A TXT property value may be at most 230 bytes (key=value is capped at 255). Any value exceeding this is suppressed (replaced with an empty string) so it does not break advertisement.