Free Audio to Video

Worked example

A 4:00 MP3 and a 3,000×3,000 square cover, on a computer. Drop both in. The page shows "Audio length 4:00" and, because the cover is within 3% of square, "Smart: 1:1 · 1080×1080 px — your cover already has this shape." A computer starts on "HD (up to 1920 px)" with "Cover image" as the visual style, so the estimate reads "Estimated render ~4:00 on this device (varies)": 240 seconds of audio × 0.5 × 2 for HD. Choose "Fast (up to 1280 px)" and the frame becomes 720×720 and the estimate 2:00. Choose "Waveform" at HD and the estimate doubles to 8:00, because every frame is drawn separately, with a moving wave along the bottom 32% of the frame. Press "Make video" and you get one MP4 named after the audio file, with the sound re-encoded as AAC at 192 kbps (about 5.5 MB of sound for 4 minutes). The finished size is shown next to the download button. Pick "60 s clips" first and you get "4 clips, up to 1:00 each", delivered as a ZIP named like song-clips.zip that holds song-part01.mp4 to song-part04.mp4.

Which settings to use, and the limits

• Choose the visual style by how long you can wait. "Cover image" holds the picture still for the whole track. It is the fast path: the picture is read once a second and repeated to 10 frames per second. "Waveform" and "Spectrum" draw a moving wave or frequency bars along the bottom 32% of the frame at 20 frames per second, in white (or dark slate when the picture under the strip is light), and the time estimate doubles. On a computer the page shows an amber warning above 15:00 of audio for "Cover image" and above 7:30 for the animated styles; on a phone the warning starts at 4:00 and 2:00. Once rendering is under way the bar shows "About 2:10 left" style estimates after the first few seconds.
• Match the shape to where the video will be posted. "Aspect ratio" offers "Smart", 16:9, 9:16, 1:1 and "Original". The frame sizes are 1280×720, 720×1280 and 720×720 on "Fast", and 1920×1080, 1080×1920 and 1080×1080 on "HD". "Smart" keeps your cover's own shape when it is within 3% of 16:9, 9:16 or 1:1. Otherwise it uses 16:9 and fills the sides with a blurred copy of the cover; the cover is never cropped. "Original" keeps any shape but is only available with the "Cover image" style, and it caps the width at 1,280 px on "Fast" and 1,920 px on "HD". A 3,000×2,000 cover comes out 1920×1280 on "HD". "Original size (slower)" removes the cap; for the fixed shapes it gives the same sizes as "HD".
• Put the title on the picture. Tick "Show title on the video" to print a title and an optional artist on the picture, each up to 120 characters. They sit along the bottom for "Cover image" and along the top for the animated styles. A long title wraps to 3 lines and the artist to 2. The text is drawn by your browser, so Chinese, Japanese, Arabic and other scripts work. If an MP3 carries ID3 tags, the title and artist are filled in for you ("Filled in from the audio file's tags."), and an embedded cover is used unless you already chose a picture. Only ID3 version 2.3 and 2.4 tags are read.
• Trim, fade and split in the same render. "Trim start (s)" and "Trim end (s)" cut the audio in steps of 0.1 second. "Fade in (3s)" and "Fade out (3s)" are 3 seconds long; the fade-out is only applied to audio longer than 3.5 seconds and needs the track length to be known. Under "Clip length", "15 s clips", "30 s clips", "60 s clips" and "90 s clips" cut the audio into equal parts (the last may be shorter) and give a ZIP of MP4s; the fade-in goes on the first clip and the fade-out on the last. With "Cover image", AAC audio (M4A or AAC files) with no fades is copied into the MP4 without re-encoding, which saves time. Anything else, and every "Waveform" or "Spectrum" video, gets its sound re-encoded to AAC at 192 kbps.
• Know the size and length limits. The audio and the picture are counted together. The page refuses them above about 2 GB on a normal computer, about 1 GB on a computer reporting 4 GB of memory or less, and about 400 MB on a phone, and shows a caution above 800 MB, 400 MB and 150 MB. The finished MP4 is built in memory, so a phone also refuses a track (or one clip, when you split) longer than 10:00 with "Cover image" and longer than 5:00 with "Waveform" or "Spectrum". A computer has no such length stop, only the amber warning. The video engine, about 31 MB, starts downloading as soon as you add the audio and is cached afterwards. Your files are processed in the browser and are not uploaded.
• No picture? Use a plain background. The link "No picture? Use a plain background" makes a dark 1280×720 background so you can export without any image. If the style was "Cover image" it switches to "Waveform" for you, so the video is not just a black still, and if the aspect was "Original" it changes it to "Smart". "Try a sample" loads a short generated melody and a sample picture so you can see the result first. The video engine starts loading when you add the audio, and a line reads "Encoder ready" when it has loaded.

Common problems and how to fix them

It says "Render cancelled. Adjust your settings and try again."

That message follows pressing "Cancel" during a render. Cancel stops the encoder, so nothing from that run is saved. Press "Make video" again; the engine reloads from the browser's cache, which is quick. If you cancelled because it was slow, pick "Fast (up to 1280 px)", keep "Cover image", trim the audio or choose a clip length before you start again.

It says "This conversion failed — the chosen format or codec may not be supported for this input. Try a different output format, or a different source file."

This tool always writes an MP4, so the part of the message that helps is "a different source file". Re-save the audio as MP3 or WAV and choose it again, and use a JPG or PNG as the cover. If you see the other wording ("...unexpected name. Try re-importing it..."), choose the file again from your device. "Fast (up to 1280 px)" with "Cover image" is the lightest combination to try.

It says "This track is 12:00, which is too long to render on a phone with this visual style (limit 10:00). Use the trim fields to render a shorter section, or open this page on a desktop computer."

"Make video" is disabled while this shows. The stop is 10:00 for "Cover image" and 5:00 for "Waveform" or "Spectrum". Either set "Trim start (s)" and "Trim end (s)" to a shorter section, or choose a clip length: the stop is applied to one clip at a time, so "60 s clips" lets a long track through as a ZIP. Switching "Waveform" to "Cover image" doubles the allowed length. A computer can render longer tracks; if it ever ends with "The browser ran out of memory processing this file", use the same remedies.

It says "This file is 2.3 GB, which is too large to process in your browser on this device (limit ~2 GB). Try a smaller file or trim a shorter clip first."

The size in the message is the audio and the cover added together, and the limit is your device's: about 2 GB, 1 GB or 400 MB. The "Trim" fields do not get around this, because the check is made on the files you load. Cut the audio shorter first, or save it as a lower-bitrate MP3, then load it again. A phone or a computer with 4 GB of memory or less has the lower limits.

It says "cover.jpg could not be read. If it is stored in Google Photos, iCloud or a cloud drive, save it to this device first, then choose it again."

Your browser could not open the picture, so the page dropped it and asks again. Choose a JPG, PNG or WebP saved on your device, or press "No picture? Use a plain background". A cover taken from the audio file's own tags that cannot be opened is skipped quietly, so you only see this message for a picture you chose.

How it compares

The three visual styles differ mainly in render time. "Cover image" is the quickest because the picture is read once a second and repeated to 10 frames per second. "Waveform" and "Spectrum" redraw every frame at 20 frames per second and are estimated at twice the time. Compared with a desktop video editor, this tool does one job: one audio file and one picture for the whole length, with optional title text, fades, a trim and a clip split. It has no slideshow of several pictures, transitions, captions or lyrics, and no bitrate or quality setting; the video is encoded with the fastest x264 preset. It does not upload to YouTube or social sites for you; it makes the MP4 and you upload it. In exchange there is nothing to install, and the whole file is built in the browser's memory, which is why phones have a length stop and the largest files can fail.