The real negotiated codec
Subscribes to the Windows Bluetooth A2DP ETW provider and reads the codec ID from the actual A2dpStreaming negotiation event — not a capability guess.
For Windows 10 & 11
See the Bluetooth codec Windows actually uses
Bluetooth Audio Codec reads the real codec negotiated between Windows and your headset — not just what the device claims to support. SBC, AAC, aptX HD, LDAC, LHDC and more, captured straight from the Bluetooth A2DP trace.
x64 ·ARM64 ·Free ·Offline installer
See it in action 
15+ codecs
identified by name
9 languages
built in
0 changes
to your Bluetooth
~50 MB
self-contained
Features
Built to read what Windows negotiated
Device settings pages only list what a headset could support. This app reads the codec from the live Bluetooth audio stream event itself.
15+ codecs named
Resolves SBC, AAC, aptX Classic, aptX HD, aptX Low Latency, FastStream, Sony LDAC, Samsung Scalable, Savitech LHDC and more. Unknown values show their raw IDs.
Native WinUI 3 + Mica
A modern Windows 11 desktop app with a Mica backdrop, accent result card, and full light & dark theme support that follows your system.
Never touches your settings
Read-only. It plays one short quiet tone to start a stream, listens to the trace, and stops. No Bluetooth pairing, codec, or audio setting is ever changed.
Principle of least privilege
The UI runs at normal integrity. Only a hidden, short-lived helper elevates to read the ETW trace, over a named pipe authenticated with a 256-bit token.
Localized in 9 languages
English, 简体中文, 繁體中文, Deutsch, Español, Français, Italiano, 日本語, and Português (Brasil) — shipped in every build.
Preview
Clean, focused, one button
A prominent codec result card, a compact status badge, and collapsible technical details — usable at 680 × 600 and beyond.
Ready
Ready
The app opens at normal permission and shows your current default output.
Detected
Detected
The negotiated codec, protocol, device, and raw IDs — captured from the A2DP trace.
How it works
From click to codec in four steps
Windows only exposes the Bluetooth codec trace to elevated processes. The app keeps the UI normal and elevates only the trace reader.
1
Open the app
It launches without a UAC prompt and shows your current default audio output device.
2
Click Detect codec
Windows asks for administrator approval just for the trace — the UI itself is never restarted or elevated.
3
A quiet tone opens a stream
A short 660 Hz tone tells Windows to open a fresh A2DP stream, which emits the A2dpStreaming event.
4
Read the negotiated codec
The helper reads the codec IDs from the event, resolves the name, and returns the result over an authenticated pipe.
Why administrator? The A2dpStreaming ETW event is only available to elevated processes. The app uses elevation solely to read this trace — nothing else.
Codec catalog
Recognized at a glance
Standard A2DP codecs and known vendor tuples are resolved to a friendly name. Anything unknown is returned with its raw IDs instead of being guessed.
Standard
SBCMPEG-1/2 Audio (MP3)MPEG-2/4 AACMPEG-D USACATRAC family
Qualcomm / CSR
aptX ClassicaptX HDaptX Low LatencyFastStreamTWS v3 AAC / MP3 / aptX
Vendor
Sony LDACSamsung HDSamsung Scalable CodecSavitech LHDC
Unknown values render as their raw hex IDs (e.g.
vendor 0x0000004F, codec 0x0001) so nothing is ever silently mislabeled. Download
Get it for Windows
Offline MSI installers with no downloader or bundled extras. Self-contained — no runtime to install separately.
System requirements
- Windows 10 version 2004 (build 19041) or later, or Windows 11
- x64 or ARM64 processor
- Administrator approval is requested only during codec detection
- A Bluetooth headset connected as the default audio output
Prefer the command line?
A single-file .NET 10 console version is also included in the repository. Run it from an elevated PowerShell and get the same codec result - with --json, --watch, and --no-tone options.
Privacy & security
Local-only by design
Detection runs entirely on your device. Nothing is recorded, uploaded, or left running.
- All detection and parsing happens locally on your device.
- No telemetry, no network requests, no audio recording or storage.
- No Bluetooth, audio, or system settings are ever modified.
- No driver, Windows service, or persistent administrator process is installed.
- The elevated helper starts only when you begin a detection, and exits when it finishes.
FAQ
Frequently asked questions
Why does detection need administrator?
Windows only exposes the Bluetooth A2DP codec trace (ETW) to elevated processes. The app's UI runs normally; only a hidden helper elevates briefly to read the trace, then exits. Canceling the UAC prompt is non-destructive.
It says “No codec event observed.” What now?
Windows didn't open or close an A2DP stream during the 30-second window. Stop all playback first, then click Detect again — the quiet tone opens a fresh stream. If your headset microphone is in use, Windows may have switched to HFP, which uses different codecs.
Does it support Bluetooth LE Audio?
No. LE Audio uses the LC3 codec over a different protocol stack and is not reported by the A2DP provider. The app detects this case and tells you LE Audio isn't supported through A2DP tracing.
What about calls and the microphone (HFP)?
Hands-Free Profile (HFP) uses CVSD or mSBC for voice, not A2DP music codecs. The A2DP event only fires for music streaming. The footer in the app explains this distinction.
Does it change my Bluetooth or audio settings?
Never. The app is strictly read-only. It plays one short quiet tone to start a stream and listens to the trace. No pairing, codec selection, or default device is modified.
Is it free and open source?
Yes. The app is free, and the full source — including the WinUI 3 desktop app and the single-file command-line version — is in the repository.
Support
Need more help?
Find troubleshooting steps, open a GitHub issue, or email the developer.