What is STREAMINFO in a FLAC file?

STREAMINFO is the mandatory first metadata block of every FLAC stream. It holds the audio fundamentals: sample rate, bit depth, channel count, total sample count and an MD5 signature of the decoded audio.

What are Vorbis comments?

Vorbis comments are FLAC's tagging system, stored in the VORBIS_COMMENT metadata block. They are simple KEY=VALUE pairs such as ARTIST, TITLE, ALBUM and DATE, plus a vendor string identifying the encoder.

Is my audio file uploaded anywhere?

No. The FLAC file is read and parsed entirely in your browser using the FileReader API. Nothing is sent to a server, so even private recordings stay on your device.

Why does the duration not match my player exactly?

Duration is computed as total samples divided by sample rate, which is the exact figure stored in STREAMINFO. Some players round to whole seconds, so small differences in the fractional part are normal.

FLAC Metadata Viewer

The FLAC Metadata Viewer parses Free Lossless Audio Codec files directly in your browser to reveal the technical details and tags embedded inside them. FLAC stores its metadata in a chain of well-defined blocks at the start of the file, so the relevant information can be read without decoding any audio. This tool extracts the STREAMINFO block and any Vorbis comment tags so you can verify sample rate, bit depth and tagging without opening a full audio editor.

How it works

A FLAC file begins with the four-byte ASCII marker fLaC, followed by one or more metadata blocks. Each block has a four-byte header: one byte holding a “last block” flag plus a 7-bit block type, then a 24-bit big-endian length. The tool walks this chain until it hits the block whose last-block flag is set.

The STREAMINFO block (type 0) is bit-packed rather than byte-aligned: 16 bits for minimum block size, 16 for maximum, 24 each for minimum and maximum frame size, then 20 bits of sample rate, 3 bits of channel count (minus one), 5 bits of bits-per-sample (minus one), and 36 bits of total sample count, followed by a 16-byte MD5 of the unencoded audio. Duration is simply totalSamples / sampleRate.

The VORBIS_COMMENT block (type 4) stores a little-endian length-prefixed vendor string, then a count of KEY=VALUE entries, each itself length-prefixed. These are the human-readable tags such as ARTIST, TITLE and ALBUM.

Tips and notes

A 48,000 Hz sample rate with 24-bit depth indicates a hi-res master; CD-quality is 44,100 Hz at 16-bit.
The MD5 signature lets tools verify that a re-encode produced identical audio.
If the file has no Vorbis comment block, it is untagged — common for FLACs ripped without metadata lookup.

Everything runs locally in your browser — your audio file is never uploaded.