For most ESP32 Bluetooth proxies, keep ESPHome’s BLE scan interval and window at their defaults. Start with esp32_ble_tracker: and bluetooth_proxy:; enable active proxy connections if Home Assistant needs to read or write device characteristics. Change connection slots only when you need more simultaneous active connections, and increase them conservatively because each slot uses memory.
Start with a minimal proxy configuration
ESPHome’s proxy uses the BLE tracker component. A typical Wi-Fi configuration follows this pattern:
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esp32:
variant: esp32
framework:
type: esp-idf
esp32_ble_tracker:
bluetooth_proxy:
active: trueAdd the network, API, and OTA settings required by your installation; ESPHome’s full example also enables logging. The active: true line is optional on ESP32 because active proxy connections are enabled by default in the current documentation, but stating it explicitly makes the intended behavior clear. See ESPHome’s Bluetooth Proxy documentation.
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A proxy can forward BLE advertisements and, when active proxy connections are enabled, support integrations that connect to a device and read or write GATT characteristics. Advertisement forwarding does not use proxy connection slots. Passive broadcast sensors therefore do not need active GATT connections just to deliver their advertisements to Home Assistant. Device and integration support varies; a proxy does not make every BLE device compatible.
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Two similarly named settings control different things:
bluetooth_proxy.activeenables active GATT proxy connections.esp32_ble_tracker.scan_parameters.activecontrols active scanning, which requests scan-response data from nearby devices.
Change connection slots only when connections are the bottleneck
ESPHome’s current ESP32 proxy documentation sets connection_slots to 3 by default. Each configured proxy slot uses approximately 1 KB of RAM, and ESPHome recommends not exceeding 5 to avoid stability and memory problems. The documented maximum is 9, but the proxy’s slot count must not exceed the BLE component’s max_connections. These are ESPHome configuration figures, not independent measurements. See the proxy reference.
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Slots matter for simultaneous active GATT connections, not for advertisement reception. Devices that stay connected can occupy slots; devices that connect briefly and disconnect release them. Before increasing the setting, identify whether Home Assistant is actually trying to maintain more concurrent connections than the proxy allows.
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Keep the BLE connection limit in step
esp32_ble.max_connections is the total simultaneous BLE connection limit shared by the tracker, proxy, and BLE server. ESPHome documents a default of 3, a range of 1–9, and roughly 1 KB of RAM per connection slot; it recommends staying at or below 5 for memory stability. If you raise connection_slots, make sure this BLE limit is at least as high, while accounting for the board’s other memory demands. ESPHome warns that the ESP32 BLE stack itself consumes significant RAM.
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Older configurations may put max_connections under esp32_ble_tracker. That option is deprecated; configure it under esp32_ble instead. The tracker documentation says the deprecated option is scheduled for removal in ESPHome 2026.10.0. Because configuration names and timelines are release-sensitive, check the documentation for the ESPHome version installed on your node before migrating older YAML. References: ESP32 BLE component and ESP32 BLE Tracker.
Usually leave scan interval and window at their defaults
ESPHome recommends the default scan parameters for most users. Changing interval or window often adds CPU and network load without a meaningful benefit. ESPHome warns that aggressive scan settings can overheat some PoE proxies and destabilize Wi-Fi proxies. In particular, a higher scan duty cycle is not a guaranteed way to improve reception.
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The BLE tracker defines interval as the time between scan windows and window as the time spent listening on a channel; the window cannot exceed the interval. With Wi-Fi configured, the default window equals the interval so Bluetooth can listen when Wi-Fi is not using the shared radio. If tuning scans made a Wi-Fi proxy unstable, restore the defaults before trying other changes. See Bluetooth Proxy guidance and the tracker reference.
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Active scanning is not active proxying
Active scanning is enabled by default. It asks nearby devices for scan-response data, which may contain additional information, but can increase battery use on those BLE devices. Passive scanning is adequate for most ongoing operation; set scan_parameters.active: false if the devices you care about do not need scan responses or you want less radio activity. This does not disable active GATT connections controlled by bluetooth_proxy.active.
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Use connection scan and coexistence settings cautiously
connection_scan_window
This setting controls listening time for scans while a BLE connection is active. ESPHome cautions that setting it close to the scan interval can leave too little radio time for active connections and cause disconnects. When Wi-Fi is configured and the regular window defaults to interval, the documented default for connection_scan_window is 30 ms. If connections drop during scanning, inspect this value rather than maximizing every scan window. See the BLE component reference.
software_coexistence
With Wi-Fi configured, software coexistence is enabled by default. It briefly prioritizes Bluetooth over Wi-Fi during initial BLE connection establishment and may improve reliability. It is available only with the Wi-Fi component; leave it at its default unless you are diagnosing a specific issue. See ESPHome’s BLE documentation.
Adjust notification and timeout limits only for specific symptoms
max_notifications
ESPHome documents a default maximum of 12 notification registrations shared across BLE connections, with a configurable range of 1–64. Raise it only when a device needs more characteristic notifications and logs show ESP_GATT_NO_RESOURCES with status 128 while notifications are being enabled.
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The documented default is 20 seconds, with a range of 10–180 seconds. ESPHome advises aligning this timeout with the BLE client’s timeout so a failed connection attempt does not occupy a proxy slot longer than necessary. Both settings are described in the ESP32 BLE reference.
Troubleshoot in an order that avoids unnecessary tuning
- Check the task. Advertisement-only devices do not require active GATT connections; integrations that read or write characteristics do.
- Undo aggressive scan changes. Restore default interval and window settings if Wi-Fi became unstable, the proxy overheats, or tuning did not help reception.
- Investigate connection drops during scans. Review
connection_scan_windowand avoid starving active connection traffic. - Check slot exhaustion. Count devices that remain connected at once, then raise proxy slots conservatively within the BLE connection limit and memory headroom.
- Match settings to log symptoms. Consider
max_notificationsfor notification resource errors; alignconnection_timeoutwith the client when connection attempts time out. - Improve placement and radio conditions. ESPHome advises placing the node near BLE devices and at least 3 meters from routers, switches, and similar equipment. Ethernet can remove Wi-Fi traffic from the ESP32’s radio.
Placement and network design are often better first moves than increasing scan duty. ESPHome’s proxy documentation includes a Wi-Fi example and a separate Ethernet example for the Olimex ESP32-PoE-ISO. That board is an example, not a requirement: choose hardware compatible with the ESPHome variant and network connection, and consider an external antenna if the selected hardware supports one.
Quick Recap
Choose settings based on connection type and network
| Situation | Settings approach | Why |
|---|---|---|
| Wi-Fi proxy, default operation | Keep scan interval and window at their defaults. | Aggressive scans can destabilize Wi-Fi, while ESPHome recommends defaults for most users. |
| Ethernet proxy | Keep defaults initially; investigate scan changes only for a specific need. | Ethernet offloads Wi-Fi traffic from the ESP32 radio, but aggressive scans can still increase load and may overheat some PoE proxies. |
| Advertisement-based sensor | Forward advertisements; no active GATT slot is needed just for broadcast data. | Advertisement forwarding is separate from active connections. |
| Integration that reads or writes GATT characteristics | Enable active proxy connections and provide enough slots for simultaneous connections. | These operations require active connections and consume slots. |
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