Does converting M4A to OGG lose quality?

Yes, some. Nearly all M4A files hold AAC, which is lossy, and Opus is lossy too, so this is a second round of compression. At 96 or 128 kbps it is often hard to hear on ordinary audio, but it cannot be undone. Keep the M4A.

Will the OGG be smaller than my M4A?

Only if you choose a lower bitrate than the M4A has. A 128 kbps M4A converted at 128 kbps comes out about the same size, and at 96 kbps about three quarters of it. If the M4A is 64 kbps, a 96 kbps OGG is bigger, and no better.

Is the OGG file Vorbis or Opus?

Opus. This page cannot write Vorbis, and many games and older programs mean Vorbis when they say OGG. Godot's documentation, as an example, names Ogg Vorbis and not Opus. Test one short file before you convert a folder.

Does it work in Safari and on iPhone?

From Safari 26 on, if the page's check finds an Opus encoder; it asks when the page opens and tells you if not. Earlier Safari has no audio encoder for the page to use, and Firefox on Android has none either. Those browsers can use the M4A to MP3 Converter instead.

No. Decoding, encoding and writing the Ogg file all happen in your browser, so the recording stays on your device. The page counts ordinary analytics events, such as a conversion finishing and the bitrate used, but never the file or its name.

M4A to OGG Converter

A free M4A to OGG converter for when a website, app or game asks for OGG and you have a phone recording or a music file in M4A. Your browser does the work on your device, so nothing is uploaded, and the result is Opus audio in an Ogg file.

Checking whether this browser can encode Opus…

Drop your M4A here or click to browse

Up to 100 MB and 30 minutes. The output is Opus audio in an Ogg container (.ogg). MP3, WAV, AAC, FLAC, AIFF and WebM work too.

The file is converted in your browser and is not uploaded. Have an OGG that will not play somewhere? The OGG and Opus to MP3 Converter turns it into an MP3.

How to convert M4A to OGG

Before you pick a file, the page looks for an Opus encoder in your browser and says so if there is none.

1
Drop the M4A
Drag the .m4a onto the converter or tap to pick it. The page goes by the file's ending and its contents, so it does not matter what type your system reports.
2
Choose the bitrate
96 kbps is preselected. Pick a lower number than your M4A has if you want the file to shrink, and turn on mono for a single voice.
3
Convert and listen
Your browser decodes the AAC audio, resamples it to 48 kHz, the rate Opus runs at, and encodes it. The page then wraps the packets in an Ogg file. Play it back once in the preview to check it.

What an M4A is, and what you give up

M4A is the usual ending for an MPEG-4 file with only audio in it. The sound inside is usually AAC, which is lossy, and sometimes Apple Lossless (ALAC), which is not.

Opus is lossy too. So converting an AAC M4A means one lossy format after another: what was dropped when the M4A was made stays gone, and a little more goes at this step. MDN warns that lossy compression is compounded by recompressing. Converting costs some quality, so do it because something needs an OGG, and keep the M4A.

What you get is always Opus inside Ogg, not Vorbis. RFC 7845 recommends the .opus ending for such a file; this page names it .ogg because that is what you asked for.

M4A, OGG and MP3 side by side

Each row is a common combination. Which one to use depends on where the file has to play.

File	Codec	Lossy	In browsers	From this page
M4A	AAC	Yes	Chrome, Edge, Safari; Firefox if the system provides AAC	Your input
M4A	Apple Lossless	No	Safari only	Input in Safari
OGG	Opus	Yes	Chrome, Edge, Firefox, Safari 18.4 or later	The output
OGG	Vorbis	Yes	Chrome, Edge, Firefox, Safari 18.4 or later	Not written here
MP3	MP3	Yes	All of them	M4A to MP3 Converter

Browser support per MDN's codec and container guides, read 4 November 2026. MDN itself says Ogg has never gained the wide support to be a first choice, so check the place the file is going.

Does the OGG come out smaller?

Only if its bitrate is lower than the M4A's. The size is the bitrate times the length, whatever went in; this table compares with a 128 kbps M4A.

Opus bitrate	Per minute	30 minutes	Compared with a 128 kbps M4A
32 kbps	234 KB	6.9 MB	25%
64 kbps	469 KB	13.7 MB	50%
96 kbps	703 KB	20.6 MB	75%
128 kbps	938 KB	27.5 MB	100%

Estimates; the Ogg pages add about one percent. 1 MB = 1,048,576 bytes. The highlighted row is the default.

Which bitrate to pick

The ranges below are the recommended Opus bitrates from RFC 7587, for full-band audio in 20 ms frames.

Speech: 32 kbps, mono on
Full-band speech is 28 to 40 kbit/s in that list. A voice has no use for two channels, so mono puts all the bits into one.
Music in mono: 64 kbps
Mono music is listed at 48 to 64 kbit/s, and this is the top of that range.
Stereo music: 96 or 128 kbps
Stereo music is listed at 64 to 128 kbit/s. Since the audio has already been through AAC, do not start low: there is less margin than from a WAV.

Browsers that can do this

Two things have to work: reading the M4A and writing Opus. The page uses the WebCodecs audio encoder, and asks it about Opus when the page opens rather than assuming.

Browser	Audio encoder (WebCodecs)	Opus here
Chrome (computer and Android)	Since version 94	Checked when you open the page
Edge	Since version 94	Checked when you open the page
Safari (Mac, iPhone, iPad)	Since version 26	Checked when you open the page
Firefox on a computer	Since version 130	Checked when you open the page
Firefox on Android	Not available	No

Per MDN's browser compatibility data for AudioEncoder, read 4 November 2026. On Safari before version 26 the page says it cannot write the file, and writes nothing else in its place.

Is your M4A someone talking?

An OGG gets the audio where it has to go, but you still have to listen to it to find anything. ParrotNotes records meetings and interviews on your phone, transcribes them and summarizes them.

Get Started Free

Related tools

M4A to OGG FAQ

Sources

M4A to OGG Converter

How to convert M4A to OGG

Drop the M4A

Choose the bitrate

Convert and listen