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.
Reading the STREAMINFO output
The STREAMINFO block is the most technically dense part of a FLAC file, and the values it contains tell you a lot about the recording:
| Field | What it means |
|---|---|
| Sample rate | The number of audio samples per second. CD audio is 44,100 Hz; hi-res masters are typically 88,200 Hz or 96,000 Hz (or higher). |
| Bit depth | Bits per sample. 16-bit is CD quality; 24-bit is used in studio masters and hi-res releases. |
| Channels | 1 for mono, 2 for stereo. FLAC supports up to 8 channels (for surround). |
| Total samples | The raw count of audio frames. Divide by sample rate for exact duration. |
| MD5 signature | A fingerprint of the raw decoded audio. If you re-encode a FLAC and the MD5 changes, the audio content has changed. |
| Min/max block size | The encoder’s frame size in samples — larger blocks compress better; smaller blocks allow finer seeking. |
A file showing 44,100 Hz and 16-bit is CD-resolution. A file with 96,000 Hz and 24-bit indicates a hi-res master that preserves more headroom than CD audio.
Common Vorbis comment tags
FLAC uses Vorbis comments for metadata. While any KEY=VALUE pair is valid, the commonly used standard fields include:
| Tag key | Typical content |
|---|---|
| TITLE | Track title |
| ARTIST | Performing artist |
| ALBUMARTIST | Album-level artist (for consistent sorting) |
| ALBUM | Album name |
| DATE | Year or full release date |
| TRACKNUMBER | Track position, often 1/12 or just 1 |
| DISCNUMBER | Disc within a multi-disc set |
| GENRE | Music genre |
| COMMENT | Free-text notes |
| REPLAYGAIN_TRACK_GAIN | Replay Gain volume normalisation value in dB |
| REPLAYGAIN_ALBUM_GAIN | Album-level Replay Gain |
| ENCODER | Software used to encode the FLAC |
The vendor string (stored before the comment entries) typically identifies the encoder — for instance reference libFLAC 1.4.3 20230623 for files encoded with the FLAC reference library.
What the MD5 is useful for
The 16-byte MD5 stored in STREAMINFO is a hash of the raw uncompressed audio data. It is not the MD5 of the FLAC file itself — it is computed on the decoded audio. This means:
- You can re-compress a FLAC at a different compression level and the MD5 in the new file should be identical, confirming the audio was not altered.
- Some archiving and library tools (dBpoweramp, EAC) use the MD5 to verify that a rip was bit-perfect.
- If you edit tags and the MD5 changes, something went wrong — FLAC tag editing should not alter the audio data or the STREAMINFO hash.
Tips
- If the Vorbis comment block is absent, the file is untagged. This is common for FLACs ripped with older software that did not do a MusicBrainz lookup.
- The tool shows all metadata blocks by type, so you can also see if the file contains a PICTURE block (embedded cover art), a CUESHEET, or SEEKTABLE.
Everything runs locally in your browser — your audio file is never uploaded or transmitted anywhere.