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Adjust bitrate

Free online tool to re-encode audio with a selected MP3 bitrate

Upload audio

Output audio

Choose a file and start processing. The output audio will appear here.

About this tool

Audio bitrate is the amount of encoded data used each second. In lossy formats such as MP3, a higher value generally retains more detail but produces a larger file; actual quality also depends on encoder, channels, source, and content complexity.

Changing bitrate requires re-encoding and cannot turn a low-rate source into high-fidelity audio. Use the tool to make delivery copies for platform limits, download speed, or storage budgets while retaining the original master.

How to use it

  1. Confirm source and constraints

    Record source parameters and the target platform’s maximum size or recommended rate.

  2. Choose the target

    Speech can be tested lower, while complex music needs a conservative reduction.

  3. Listen and compare size

    Inspect critical passages and download size, choosing the version that meets the quality floor.

Supported range and limits

Available steps
Commonly 96 / 128 / 192 / 256 / 320 kbps; pick what the target system asks for
Encoding mode
Constant bitrate (CBR), so the data per second is fixed and the size is predictable against an upload limit
Raising the bitrate
Does not improve quality, only size; information absent from the source cannot be reconstructed
Duration and channels
Unchanged; only the data rate differs
Size arithmetic
Size ≈ bitrate ÷ 8 × seconds, which you can invert to find the step that fits a limit
Where it runs
FFmpeg compiled to WebAssembly in your browser; the file is never uploaded

When you would use it

  • Standardizing delivery parameters

    Output several spoken tracks at one bitrate for predictable platform handling and size.

  • Reducing mobile transfer

    Create a smaller copy for playback on constrained networks.

  • Meeting a platform's upload specification

    Some podcast hosts and content systems state a required bitrate, and the file has to be re-encoded to that number to pass validation.

What to know before you start

  • Converting 64 kbps to 320 kbps only enlarges the file and cannot restore detail.
  • The same number across different codecs does not imply the same quality.
  • Constant bitrate makes size predictable, while content-aware encoding efficiency varies by passage.

Related concepts

kbps
Kilobits per second, a unit of thousands of encoded bits used each second.
re-encoding
Decoding an existing file and generating audio again with new encoding settings.

Frequently asked questions

How does changing bitrate affect the file?
A higher bitrate means better quality and a larger file; a lower one means a smaller file and reduced quality. The tool re-encodes the MP3 at your chosen bitrate.
Does changing bitrate upload my file?
No. Re-encoding runs locally in your browser and the audio is never uploaded.
How do I pick a common bitrate?
Speech works at 64-128kbps and music commonly uses 192-320kbps; balance size and quality for your use case.
Is there any point going from 128 to 320 kbps?
Only if a downstream system insists on 320. Quality does not improve; high frequencies already discarded do not return because more bits were allocated. You simply get a larger file.
CBR or VBR?
Output here is constant bitrate, which makes size exactly predictable and is the most compatible. VBR usually sounds better at the same average rate, but some older devices and streaming systems handle it poorly.
How do I work out which step I need?
Size ≈ bitrate ÷ 8 × seconds. To fit ten minutes under 10 MB: 10 × 1024 × 8 ÷ 600 ≈ 136 kbps, so 128 kbps leaves comfortable headroom.

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