Free MP4 to AAC Converter: No Sign-up, Files Never Uploaded
Convert MP4 to AAC free, right in your browser. There is no sign-up or login, no watermark, and nothing is uploaded: your videos never leave your device.
The video and audio tracks are read, decoded and encoded again for the AAC container, which takes real work from your processor. AAC uses lossy compression, so each save trades some detail for a smaller file.
This pair runs on code that is already in the page, so there is no extra engine to download.
- Free
- No sign-up
- Never uploaded
- No watermark
Your files are converted on your device and never uploaded.
How to convert
- Add your MP4 files by dragging them onto the converter or by using the file picker.
- Check that AAC is the selected target format; it is already chosen on this page.
- Open the options if you want to change resolution, frame rate and quality, or keep the defaults.
- Press Convert and watch the progress shown for each file.
- Download each result, or take them all together as one ZIP when you converted several files.
Features
- Reads .mp4 and writes .aac.
- Free, with no watermark added to the result.
- No sign-up and no login.
- Your files are never uploaded and never leave your device.
- Batch conversion with a ZIP download for several results.
- The input is recognised by its content, not only by its file name.
Supported formats
About the formats
About MP4
The most widely supported video format: plays on phones, browsers, TVs and editors.
Usually H.264 video with AAC audio.
Based on Apple’s QuickTime format and standardised by MPEG.
About AAC
Advanced Audio Coding: the successor to MP3 with better quality at the same bitrate.
This is the raw AAC stream; the same audio inside an MP4 container is M4A.
MP4 vs AAC
MP4 uses lossy compression; AAC uses lossy compression.
MP4 does not support transparency, and AAC does not.
MP4 files use the .mp4 extension and AAC files use .aac, so the converted file gets a new name with the new extension.
Privacy: how it works
- Your MP4 files stay on your device. The page reads each file with the browser's file API, converts it with code running in the tab, and hands the result back as a download. No upload happens, so there is no copy of your file on our servers to protect, delete or leak.
- There is nothing to sign up for and no login. The converter does not ask for an email address, and it does not need to know who you are to do its job.
- You can check the claim yourself: open your browser developer tools, watch the Network tab while a file converts, and you will see no request that carries your file.
Tips
- Try a short clip first to check quality and size before you convert a long video.
- Keep the original resolution unless you need a smaller file; shrinking the frame is the quickest way to cut size.
- Close other heavy tabs while converting, because the work uses your own memory and processor.
- Convert one large file at a time on a phone or a low-memory computer.
- AAC uses lossy compression, so each save trades some detail for a smaller file.
- This page converts one way only; AAC files cannot be turned back into MP4 here.
Frequently asked questions
Is it really free?
Yes. There is no price, no trial, no credit card and no watermark added to your results. Ulkaa Tool does the conversion with your own device, so there is no server bill to pass on to you.
Are my files uploaded?
No. Your MP4 files are read and converted inside your browser and are never sent to Ulkaa or to anyone else. The result is created on your device and you save it from there.
Do I need an account?
No. There is no sign-up and no login. Open the page, add your files and convert. An Ulkaa account is not needed for anything on this tool.
Is there a file size limit?
No limit is set by us. The real limit is your device: the conversion uses your own memory and processor, so very large files can be slow or fail on a weak phone or an older computer. Close other heavy tabs and convert MP4 files one at a time if a big batch struggles.
What is the difference between MP4 and AAC?
MP4 uses lossy compression; AAC uses lossy compression. MP4 does not support transparency, and AAC does not. MP4 files use the .mp4 extension and AAC files use .aac, so the converted file gets a new name with the new extension.
Can I convert many MP4 files at once?
Yes. Add as many files as your device can handle. Each one is converted on its own and you can download them one by one or as a single ZIP.
Will anything be lost when I convert MP4 to AAC?
AAC uses lossy compression, so each save trades some detail for a smaller file.
Can I convert AAC back to MP4?
Not on this page. This conversion goes one way. Open the AAC page to see which formats it can be converted to.