# Compress audio and MP3 files

Make audio files small enough to email, upload, or send in a chat.

## What makes a file big

Three things set an audio file's size: how long it is, its bitrate, and whether it's stereo or mono. Bitrate is how much data each second of sound gets, in kilobits a second (kbps). A WAV isn't compressed at all, so a minute takes about 10 MB; an MP3 leaves out detail people rarely hear, and the lower its bitrate, the more it leaves out.

Email, chat apps, and upload forms each set their own size limit, and they change them from time to time, so check the one you're sending to. Then work back from it: a 10-minute recording at 64 kbps is about 4.8 MB, and at 32 kbps about 2.4 MB, which suits only speech.

Tool: Convert (`convert_audio`). The same tool's other pages: https://audo.ai/audio-converter.md, https://audo.ai/mp4-to-mp3.md, https://audo.ai/extract-audio-from-video.md, https://audo.ai/m4a-to-mp3.md, https://audo.ai/wav-to-mp3.md, https://audo.ai/mp3-to-wav.md, https://audo.ai/mov-to-mp3.md, https://audo.ai/ogg-to-mp3.md, https://audo.ai/flac-to-mp3.md, https://audo.ai/webm-to-mp3.md, https://audo.ai/aac-to-mp3.md, https://audo.ai/mp4-to-wav.md, https://audo.ai/m4a-to-wav.md, https://audo.ai/mp3-to-ogg.md. Price: 1 credit a minute of input for whole files, charged only when a job succeeds.

## Free API

```bash
curl -F file=@lecture.mp3 -F format=mp3 -F bitrate_kbps=64 https://audo.ai/api/try/convert -D response.headers -o response.body
```

Read response.headers and response.body before naming media. Handle 202, 200 JSON and errors with the complete response client at https://audo.ai/docs/api#responses.

Free for the first hour of each file, 10 times a day per person, with no key or account. Uploads up to 100 MB, 2 at once from one address. The response is the result itself; a job that runs longer than about 30 seconds returns 202 with a link to check on it. With an API key (`-H "Authorization: Bearer $AUDO_API_KEY"`), omitting free runs the whole file with credits if the balance covers it, otherwise the free portion if quota remains. Set free=true to prohibit spending; for paid whole files use free=false with an approved positive max_credits. Details: https://audo.ai/docs/api.md

## Options

Form fields with the same names as the MCP tool's inputs:

- `format`: The format to convert to: mp3, wav, m4a, flac, ogg, or opus. Default mp3.
- `bitrate_kbps`: The bitrate for mp3, m4a, ogg, or opus, in kbps (16 to 320), such as 128. Default: chosen for the format.
- `sample_rate`: The sample rate in Hz, such as 44100. Default: the input's.
- `channels`: mono or stereo. Default: the input's.

## Languages

Any language: it works on the sound, not the words.

## From an assistant (MCP)

Add https://audo.ai/mcp and sign in (setup for each assistant: https://audo.ai/setup.md). The tool is `convert_audio`:

> Converts a file to another audio format, or pulls the audio out of a video. Use it when the person needs MP3, WAV, M4A, FLAC, OGG, or Opus. Set free to true to do the first hour at no cost, up to 10 times a day; otherwise it costs 1 credit a minute. Returns job_id; then call get_job.

Example: "Use Audo to compress lecture.mp3 to a 64 kbps mono MP3."

## More

- Every tool: https://audo.ai/llms.txt
- OpenAPI: https://audo.ai/api/openapi.json
- This page for people: https://audo.ai/compress-audio