Home Assistant Not Discovering New Devices? How to Fix It
When Home Assistant stops auto-discovering new devices, the cause is almost always the network between them — not Home Assistant itself. Auto-discovery relies on broadcast and multicast traffic (mDNS/Zeroconf, SSDP, and DHCP), which routers and access points often block or fail to forward between subnets and Wi-Fi bands. The fix is usually to put Home Assistant and the new device on the same network segment, confirm discovery traffic isn't being filtered, and reload the relevant integration. Below is a structured way to find and fix the break.
Start here: confirm what “not discovering” means
Before changing settings, narrow the problem. There are three distinct failures that people lump together:
- No automatic suggestion. The device works but never pops up under Settings → Devices & Services. This is a discovery-traffic problem.
- The integration can't be added at all. You search for it manually and it errors out or times out. This points to the integration, credentials, or cloud connectivity.
- The device isn't on the network yet. It never finished its own onboarding (Wi-Fi join, pairing mode), so nothing is there to discover.
Rule out the third case first by checking whether the device shows up in your router's client list. If it isn't getting an IP address, the problem is the device joining Wi-Fi, not Home Assistant. Our guide to fixing a smart device that won't connect covers that onboarding step.
1. Put Home Assistant on the same network as the device
This is the single most common fix. Auto-discovery protocols are not routed across subnets by default:
- mDNS / Zeroconf (used by Matter, ESPHome, HomeKit-style devices, Shelly, and many others) is link-local multicast. It does not cross a router into another subnet unless the router is specifically configured to reflect it.
- SSDP / UPnP (used by many Wi-Fi devices) is broadcast/multicast and behaves the same way.
- DHCP-based discovery watches for new devices requesting addresses on the local broadcast domain.
If Home Assistant lives on your main LAN and you joined the new gadget to a guest network or a separate IoT SSID, they're isolated by design and discovery will silently fail. The simplest fix is to temporarily join the device to the same SSID/subnet as Home Assistant to complete setup. If you intentionally segment your network, see our notes on setting up a smart-home SSID the right way.
- 1Check the device has an IP in your router’s client list
- 2Confirm Home Assistant and the device share the same subnet/VLAN
- 3Make sure mDNS/multicast and client isolation aren’t blocking traffic
- 4Reload the integration or restart Home Assistant to re-trigger discovery
- 5Add the integration manually by IP if auto-discovery still fails
2. Stop your network from filtering discovery traffic
Even on one subnet, several router and access-point features quietly kill discovery. Check each:
| Setting | Why it breaks discovery | What to do |
|---|---|---|
| AP / client isolation (“guest mode”) | Blocks device-to-device traffic, so Home Assistant can't see the device | Disable it on the SSID the devices use |
| mDNS reflector / IGMP snooping | When misconfigured, drops multicast instead of forwarding it | Enable mDNS reflection if devices span bands/VLANs; otherwise keep devices together |
| 2.4 GHz vs 5 GHz separation | Some APs isolate bands; multicast may not cross them | Confirm both are on the same VLAN/bridge |
| Wireless “smart connect” / band steering | Can shuffle a device onto an isolated band mid-setup | Temporarily pin the device to 2.4 GHz |
Most smart-home gear is 2.4 GHz-only, which matters because the band is crowded and easily disrupted — see 2.4 GHz vs 5 GHz for smart-home devices. If the network itself is unstable, discovery will be intermittent at best; our Wi-Fi improvement guide is the better starting point in that case.
3. Re-trigger discovery and check Home Assistant's side
Home Assistant scans for devices at startup and periodically, so a freshly added gadget may not appear instantly. Force the issue:
- Go to Settings → Devices & Services and look for newly discovered entries at the top.
- Use the overflow menu to reload the relevant integration, or restart Home Assistant to run a fresh discovery pass.
- If you run Home Assistant in Docker, confirm it uses
hostnetwork mode. In bridge mode, mDNS and broadcast discovery generally won't reach the device — this is a frequent, well-documented cause on the community forums. - Check Settings → System → Logs for discovery or integration errors that name the device or protocol.
If automatic discovery still won't cooperate, add the integration manually. Most integrations let you enter the device's IP address directly, which bypasses multicast entirely. Pair that with a DHCP reservation so the address doesn't change later and break the connection.
4. Matter and Thread have extra requirements
Matter discovery uses mDNS over IPv6, so everything above applies plus a few specifics. According to the Connectivity Standards Alliance, commissioning a Matter device requires a commissioner (the Home Assistant Matter server or a compatible controller), and the device and controller must share an IP path. Thread devices additionally need a Thread border router on your network to bridge the Thread mesh to your LAN.
- Confirm IPv6 is enabled on your network — disabling it is a common reason Matter devices never appear.
- A Matter device can only be commissioned by one fabric at a time during initial setup; if it's already paired to another ecosystem, use that app's “share/add to another platform” flow to generate a new pairing code.
- For Thread, make sure a border router is online and that its network credentials are shared with Home Assistant.
If a hub or border router keeps dropping off, discovery will fail intermittently — see how to stabilize a hub that keeps disconnecting.
Frequently asked questions
Why does Home Assistant discover some devices but not others?
Different devices use different discovery protocols. A device that uses DHCP discovery may appear while one relying on mDNS does not, because your network forwards one type of traffic but filters the other. Mixed results usually point to multicast being blocked rather than a Home Assistant fault.
Do I have to use auto-discovery at all?
No. Auto-discovery is a convenience. Nearly every integration can be added manually — typically by entering the device's IP address or signing into the manufacturer's cloud account. If discovery is unreliable on your network, manual setup with a reserved IP is often more dependable.
I moved my devices to a separate IoT network and discovery stopped. Why?
Separate networks (VLANs or guest SSIDs) are isolated by design, and discovery protocols don't cross that boundary on their own. You either need to keep Home Assistant and the devices on the same segment, or configure an mDNS reflector and matching firewall rules between the segments.
Could a power outage have caused this?
It can. After an outage, devices and routers may rejoin in a different order or land on a different band, and IP addresses can shift. Our guide to devices offline after a power outage walks through restoring them in the right sequence.
