# Audio File Requirements

Before Cloud Voice will accept an audio file you upload, the file has to satisfy a few rules for its name, size, and encoding. Review the requirements below so your file imports cleanly into the PBX (Private Branch Exchange, the phone system that runs your extensions and call routing) on the first try.

## When you upload audio

Several features let you replace the built-in audio with a recording of your own. You supply a custom file when you set up any of these:

- Voicemail greetings (the message callers hear when they reach voicemail)
- Music on Hold (MoH) playlists stored on the PBX
- Custom system prompts (spoken messages the system plays during a call flow)
- Custom ringtones

:::note
"Stored on the PBX" MoH means the audio lives on the system itself, as opposed to a live stream or an external source. That is why it has to meet the same file rules as every other upload.
:::

## Requirements

Any file you upload must meet all of the following:

| Item | Requirement |
| --- | --- |
| File name | Must not include special characters. |
| File size | 8 MB maximum. |
| File format | `.wav`, `.mp3`, or `.gsm`, encoded as one of:<br />- PCM, 8 kHz, 16-bit, 128 kbps<br />- A-law (G.711), 8 kHz, 8-bit, 64 kbps<br />- u-law (G.711), 8 kHz, 8-bit, 64 kbps |

:::caution
The name and size are hard limits. A file whose name contains special characters (anything other than letters, numbers, spaces, hyphens, or underscores, such as `/ \ : * ? " < > |` or accented characters), or one larger than 8 MB, is rejected at upload. Rename or shrink the file before you try again.
:::

:::note
The listed encodings are all standard narrowband telephone audio: mono, sampled at 8 kHz. PCM (Pulse Code Modulation) is uncompressed; A-law and u-law are the two companding schemes defined by the G.711 telephony codec (A-law is common in Europe, u-law in North America). Any of the three plays back correctly, so you do not need to match a specific one.
:::

:::tip
If your file does not match one of the supported encodings, [convert it first](/pbx/administrator-guide/convert-audio-files/) and then upload the converted version.
:::