MP3 Duration and Bitrate Checker
Drop in an MP3 to read its first audio frame: the bitrate in kbps, the sample rate, the MPEG version and layer, the channel mode, whether it is variable or constant bitrate, and an estimated playback length. The file is parsed entirely in your browser and never uploaded.
How to check an MP3's bitrate and duration
- Drag an MP3 onto the box, or click browse to pick one.
- Read the bitrate, sample rate, layer, channel mode, and VBR or CBR.
- Check the estimated duration computed from the file and its bitrate.
Examples
A typical music download
track.mp3 (a standard 128 kbps file)
MPEG1 Layer III, 128 kbps, 44100 Hz, Stereo, CBR, about 3:30
Frequently asked questions
Is my MP3 uploaded anywhere?
No. The file is read and parsed entirely in your browser using JavaScript. Nothing is sent to a server, so your audio stays on your device.
How does it read the bitrate without playing the file?
Every MP3 is a series of frames, each starting with a four-byte header. The tool skips any ID3 tag, finds the first frame, and decodes the header's bitrate, sample rate, layer, and channel fields against the standard MPEG tables.
What is the difference between VBR and CBR?
CBR (constant bitrate) uses the same bitrate for every frame. VBR (variable bitrate) changes it to save space on simpler passages. The tool detects a Xing or VBRI header to tell which one you have.
Why is the duration an estimate?
For VBR files with a Xing or VBRI frame count the duration is exact. For CBR files it is computed from the file size and bitrate, which is accurate to within a fraction of a second for a well-formed file.
What do MPEG version and layer mean?
MPEG1, MPEG2, and MPEG2.5 are audio standards that set the available sample rates. Layer III is what people call MP3; Layers I and II are older and rarer. The header encodes both.
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