Drop an audio file into this inspector and it reports the codec, the average audio bitrate, the nominal rate from the header where the format has one, the sample rate, channels and bit depth. MP3, M4A, FLAC, WAV and OGG headers are read locally in your browser; the file never leaves your device. The point of knowing your audio bitrate: a Bluetooth link re-encodes whatever you play into its negotiated codec, so what actually travels is capped by that codec's payload, and the published ceilings sit just below the tool.
Average bitrate is file size divided by duration, the honest whole-file number. Nominal bitrate comes from the codec header where the format provides one.
Reference figures on this page were checked October 2026. The tool runs locally in your browser: files are parsed in the page and never uploaded.
How the audio bitrate inspector works
The inspector reads the file's own headers, the same fields a player reads. MP3 frames are walked for the first sync word, which yields the layer, the nominal bitrate and the sample rate, and the Xing frame, when present, gives the true frame count of a VBR file. FLAC files carry a STREAMINFO block with sample rate, channels, bit depth and total samples. WAV is read from its fmt chunk, M4A and MP4 from their moov box, and OGG from the Vorbis or Opus identification header.
Two bitrate numbers are reported, and they mean different things. The average bitrate is file size divided by duration, the honest whole-file figure that includes every byte. The nominal bitrate comes from the codec header where the format provides one: an MP3's encoded rate for that first frame, with a VBR flag when the Xing header says the rate varies. When headers cannot be parsed, the browser's own decoder recovers duration and sample rate, and the tool says so instead of guessing.
What your file is up against over Bluetooth
A Bluetooth audio link does not pass your file through. The source device re-encodes the stream into the codec the link negotiated, so the negotiated codec's payload is the ceiling on what travels, whatever the file says. These are the published ceilings:
| Bluetooth codec | Published payload | Source / as of |
|---|---|---|
| SBC | 127 to 345 kb/s across the recommended ladder; 328 kb/s at the High Quality joint-stereo setting, 44.1 kHz | A2DP 1.3.2, 2026-09-22 |
| aptX | 352 kbps, fixed | aptX official page, 2026-09-22 |
| aptX HD | 576 kbps | aptX HD official page, 2026-09-22 |
| aptX Adaptive | Typically 279 to 420 kbps, dynamic | aptX Adaptive official page, 2026-09-22 |
| LDAC | 330 / 660 / 990 kbps modes | Sony LDAC site, 2026-09-22 |
| AAC | No Apple-published rate; 320 kbps default in Android's A2DP source; Apple devices observed transmitting 256 kbps | AOSP a2dp_aac.cc + Archimago rig, 2026-09-22 |
Compare your file's average bitrate against the row for the codec your chain uses. A lossless rip usually carries more data than any lossy payload in this table, and only LDAC's top mode reaches the same range; the numbers above and the sample-rate effects on them are compiled, with rigs and caveats, on the codec bitrate bench.
Reading your result
- Average above the ceiling. The link re-encodes the stream down to its negotiated payload. The extra bits in the file cost storage, not fidelity over that link.
- Average below the ceiling. The codec still encodes within its own ladder or mode; a smaller file does not force a smaller payload, and bitrate alone was never the quality metric anyway.
- Bit depth and sample rate. Useful for knowing what you have; what survives the link is set by the codec chain, and the hi-res caveat is stated plainly in our Tidal over LDAC page.
FAQ
No. The file is read with the browser's local file reader and parsed in the page. Nothing is sent to a server, the tool works offline once the page has loaded, and closing the tab discards everything.
Because a Bluetooth audio link re-encodes rather than passes through. Whatever the file's bitrate, the source device encodes the stream into the codec the link negotiated, and that codec's payload is the ceiling. Our page on Tidal over LDAC states the same caveat for streaming services: Bluetooth stays a lossy re-encode, and the full resolution of the file survives only on paths that do not re-encode.
Payload, not quality. The published ceilings run from SBC's 127 to 345 kb/s ladder up to LDAC's 990 kbps mode, and one measurement author found Apple's 256 kbps AAC measuring better than aptX HD and at least equivalent to LDAC above 900 kbps, because the encoder does the rest. Anything above the negotiated ceiling is re-encoded down to it, so there is no prize for an oversized file.
MP3 (CBR and VBR, with the Xing frame count), M4A and MP4 (AAC, ALAC and FLAC-in-MP4 tags), FLAC, WAV and OGG (Vorbis and Opus). Other formats fall back to the browser's own decoder, which recovers duration, sample rate and channel count but not a codec name.
blafili B3 Bluetooth Receiver
XLR, RCA, optical and coax outputs with an OLED front panel, built on the QCC5125 + ES9018K2M platform. A wired amp or receiver, put on a wireless source.
- Bluetooth SIG, A2DP 1.3.2: Table 4.7 recommended SBC parameter sets, bitpools 19/18/35/33/31/29/53/51 giving 127/132/229/237/193/198/328/345 kb/s across 44.1/48 kHz and mono/joint stereo. bluetooth.com/specifications/specs/advanced-audio-distribution-profile-1-3-2/, accessed 2026-09-22, quoted from our bitrate bench.
- Qualcomm official pages: aptX 352 kbps (48 kHz sampling); aptX HD 576 Kbits; aptX Adaptive "Typically, 279kbps to 420kbps". aptx.com, accessed 2026-09-22, quoted from our bitrate bench.
- Sony LDAC official site: 330/660/990 kbps modes. sony.net/Products/LDAC/, accessed 2026-09-22, quoted from our bitrate bench.
- AOSP a2dp_aac.cc: A2DP_AAC_DEFAULT_BITRATE 320000. android.googlesource.com/platform/packages/modules/Bluetooth/, accessed 2026-09-22; observed Apple AAC in practice at 256 kbps per Archimago Parts I and II, quoted from our bitrate bench.