What is the RIFF/WAVE format?

WAV is a RIFF (Resource Interchange File Format) container. It begins with the ASCII tag RIFF, a 4-byte file size, then WAVE, followed by sub-chunks. The fmt chunk holds the audio parameters and the data chunk holds the raw samples.

How is the duration calculated?

Duration in seconds equals the data chunk size in bytes divided by the byte rate, where byte rate is sampleRate × channels × (bitDepth / 8). For example a 44100 Hz, 16-bit stereo file has a byte rate of 176400 bytes per second.

What does the audio format number mean?

The format code in the fmt chunk identifies the encoding: 1 is uncompressed PCM, 3 is IEEE float, 6 is A-law, 7 is mu-law, and 65534 is WAVE_FORMAT_EXTENSIBLE. The inspector labels the common codes for you.

Why might the fmt chunk not be right after WAVE?

The WAV spec allows other chunks (like LIST or fact) before fmt or data. The inspector walks the chunk list by reading each chunk ID and size, so it finds fmt and data wherever they appear.

Is the audio uploaded to a server?

No. The header is parsed entirely in your browser with the FileReader and DataView APIs. No bytes are sent anywhere, so the tool works offline and keeps your audio private.

WAV Header Inspector

Decode the technical header of a WAV file — its sample rate, channel count, bit depth, encoding and exact duration — without any player or upload. The inspector reads the RIFF/WAVE structure directly with the browser’s DataView API and stays entirely on your device.

How it works

A WAV file is a RIFF container. The first 12 bytes are the ASCII tag RIFF, a little-endian 4-byte total size, and the ASCII tag WAVE. After that comes a sequence of chunks, each one a 4-character ID, a little-endian 4-byte size, and that many bytes of payload (padded to an even length).

The two chunks that matter are:

fmt   → audio parameters
  audioFormat  (2 bytes)  1=PCM, 3=float, 6=A-law, 7=mu-law, 65534=extensible
  numChannels  (2 bytes)
  sampleRate   (4 bytes)
  byteRate     (4 bytes)  = sampleRate × channels × bitDepth/8
  blockAlign   (2 bytes)  = channels × bitDepth/8
  bitsPerSample(2 bytes)

data  → the raw samples; its size gives the audio payload length

The inspector walks the chunk list rather than assuming a fixed layout, so it correctly handles files that place LIST or fact chunks before fmt or data.

Duration

Playback length comes straight from the data chunk:

duration (s) = data chunk size (bytes) ÷ byteRate

Because byteRate = sampleRate × channels × bitDepth / 8, a 10-second 44.1 kHz 16-bit stereo clip has a data chunk of 10 × 44100 × 2 × 2 = 1,764,000 bytes.

Tips

A mismatch between the stored byteRate and sampleRate × channels × bitDepth/8 usually means a malformed or non-standard encoder — the inspector shows both so you can compare.
Format code 65534 (extensible) wraps a real sub-format GUID; the bit depth and channels are still valid in the fmt chunk.
Very large declared sizes that exceed the actual file length indicate truncation or a streaming WAV written before the final size was known.