MP3 to MP4: put a picture to your audio.

At a glance

How to convert an MP3 to MP4 for YouTube

Drop the MP3 above. Leave the shape on 16:9, pick a picture, check the title, and press Make the MP4. The file downloads when it is ready, and you upload that to YouTube Studio like any other video. YouTube has no "upload audio" button; a still picture under the sound is how every music channel, podcast clip and lyric-free upload you have seen was made, and a 1920×1080 frame is what the player is shaped for, so there are no black bars on a desktop.

The page opens the codec once (a 30 MB download that the browser keeps), so the first video takes longer than the next. After that, the work is mostly the sound: the picture is turned into two seconds of video and that clip is repeated under the audio without being encoded again, which is why a long track does not take proportionally long.

Your artwork, or a cover drawn for you

My own image takes a single JPG, PNG or WebP. A square album cover in a 16:9 frame would leave two empty bands, so by default the whole picture sits in the middle on a blurred, darkened copy of itself, the look most music uploads use. "Fill the frame" crops it instead, which suits a landscape photo. Drop the picture together with the audio, or choose it afterwards.

A generated cover is for when you have no artwork: a gradient in one of five colour sets, the title (taken from the file name, editable) in large type, an optional second line for the artist, show or date, and the waveform of your actual track drawn across it. The waveform is static: it shows the shape of the whole piece, loud parts and quiet parts, rather than moving with the sound.

Sizes for YouTube, Instagram, TikTok and Shorts

16:9 at 1920×1080 is for a normal YouTube video and for anything watched on a computer or TV. 1:1 at 1080×1080 is the Instagram and Facebook feed post. 9:16 at 1080×1920 is the vertical shape of YouTube Shorts, Instagram Reels and TikTok, and the text and waveform move up so the app's own buttons do not cover them. Shorts must be three minutes or less, so cut a longer track to the part you want with the audio cutter first; Reels and TikTok change their own limits often enough that it is worth checking the app before a long upload.

What happens to the sound

MP4 carries AAC audio, which every platform accepts. If your file is already AAC (most M4A files, and audio saved from an iPhone), it is copied into the MP4 untouched. Anything else is encoded once to AAC at 320 kbps, the top of the range. YouTube, Instagram and TikTok all re-encode every upload for streaming, so what you give them is the best copy viewers will ever hear from; a 320 kbps AAC made from a 320 kbps MP3 is not where the quality goes. If you are starting from a WAV or FLAC master, upload from that rather than from an MP3 of it.

Check the level before you post. A quiet podcast or a home recording will sound weak next to everything else in the feed; the loudness normalizer brings it to the -14 LUFS that YouTube and Spotify play at, and the result can go straight back into this page.

Several tracks at once

Drop a whole album or a run of episodes and each track becomes its own MP4 with the same picture and settings, titled from its file name. To post a full album or a DJ set as one long video instead, join the tracks into one file with the audio joiner and bring that here.

What it can't do

There is one picture per video: no slideshow, no moving visualiser and no scrolling lyrics. For words on screen that follow the audio, make the MP4 here and then run it through add subtitles to video, which writes timed captions from the speech or singing. Making a video does not change who owns the music: YouTube's Content ID matches the sound, not the picture, so a commercial song will be claimed whatever image is on it. And very long audio is limited by memory, since the whole file is held in the tab while the MP4 is written; an hour of MP3 is fine on a laptop, while several hours of WAV is better cut into parts.