HandBrake - The Best Free Converter That Most People Don't Know About
HandBrake is free, open source, runs on Windows, macOS, and Linux, and has been maintained actively for nearly two decades. It converts almost any video format to MP4, MKV, or WebM, and the presets are well-designed enough that you don't need to understand codec settings to get good results. There's a YouTube preset, a Web preset, presets for Apple devices, and a general-purpose "Fast" preset for most situations.
The interface isn't beautiful. It's functional, which is what matters. You drag a file in, pick a preset or set your own output settings, and hit Start Encode. For simple format conversion, the whole process takes under a minute to set up. The encoding itself depends on file length and your computer's processing power.
HandBrake handles batch conversions, which is useful if you have many files to convert at once. Add multiple files to the queue, set the output folder, and let it run. For larger conversion jobs this is genuinely time-saving compared to processing files one at a time through a web tool.
The one thing HandBrake doesn't do: it can't convert encrypted DVDs or protected content. It processes what the operating system can access. This is a deliberate legal position by the HandBrake team, not a technical limitation.
VLC Media Player - Most People Don't Know It Converts
If you have VLC installed - and most people do, because it plays absolutely everything - you already have a video converter. Go to Media, then Convert/Save, add your file, pick an output format, and click Start. VLC uses FFmpeg under the hood and handles a wide range of format conversions reasonably well.
VLC's conversion isn't as refined as HandBrake's. The preset options are fewer, the quality control is less granular, and it doesn't have the same batch processing capability. But for a quick one-off conversion when you just need an MP4 and don't want to download anything new, VLC is already there. Fast, free, no sign-up, no ads.
FFmpeg - Powerful, Requires Command Line, Worth Learning
FFmpeg is the underlying technology that most free video tools use. HandBrake runs FFmpeg. VLC uses FFmpeg. A significant portion of the video processing you do online goes through FFmpeg somewhere in the chain. Learning to use it directly gives you more control and often faster results than going through a graphical interface.
The basic syntax for converting an MKV to MP4 is: ffmpeg -i input.mkv -c:v copy -c:a copy output.mp4. That particular command remuxes the file without re-encoding - just changing the container format - which is fast and lossless when the codec inside the MKV is already H.264 (which it usually is).
To extract just the audio as an MP3: ffmpeg -i input.mp4 -q:a 0 -map a output.mp3. To convert video to a specific resolution: ffmpeg -i input.mp4 -vf scale=1920:1080 output.mp4. The documentation is extensive and there are good quick-reference guides. If you work with video regularly, spending an afternoon learning the basics of FFmpeg pays off over and over.
Installation on Windows: download the binary from ffmpeg.org, extract it, and add the bin folder to your system PATH. On macOS, Homebrew makes it one command: brew install ffmpeg. Linux: most package managers have it.
Online Converters That Aren't Terrible
Not everyone wants to install software for a one-off conversion. The online options range from genuinely useful to malware-adjacent. Two that I've found reliable: CloudConvert and Convertio.
CloudConvert supports a huge range of formats, processes quickly, and doesn't require an account for small files. The free tier allows a certain number of conversion minutes per day. For occasional use, this is enough. Larger files or frequent use requires a paid plan, but the pricing is reasonable and the output quality is good.
Convertio is similar - broad format support, decent speed, no mandatory account for basic use. Both of these upload your file to their servers for processing, which is worth knowing if you're converting anything sensitive. For converting a publicly available video you downloaded, this is fine. For anything private or confidential, local tools are the better choice.
Converting Video to Audio (MP3, AAC, FLAC)
Extracting audio from a video is a very common need and it works through the same tools. HandBrake has audio-only output options. FFmpeg is the most flexible (the command I gave earlier handles this). Online: CloudConvert handles audio extraction cleanly.
One thing to understand: converting a lossy audio format to another lossy format degrades quality slightly with each conversion. If you extract MP3 audio from a video that already had compressed audio, then convert that MP3 to AAC, you've done two generations of lossy compression. For most listening purposes the difference is inaudible. For anything where audio quality actually matters - music production, podcasting, anything that'll be mixed or processed further - extract to FLAC or WAV to preserve the source quality, then compress at the end of the chain.
File Size After Conversion - What to Expect
File size after conversion depends almost entirely on whether you're re-encoding or just remuxing. Remuxing (changing the container without changing the codec) produces output files nearly identical in size to the original. Re-encoding to a different codec or different settings changes the size significantly.
Converting MKV to MP4 by remuxing (the FFmpeg copy command I mentioned) gives you a file almost identical in size because you're just changing the container, not re-encoding the video. Converting a large AVI to MP4 with H.264 encoding will dramatically reduce the file size because AVI with raw or older codec video is much less efficiently compressed than H.264.
If you want to reduce file size specifically, reduce the video bitrate in your encoder settings. HandBrake has an RF (quality) slider - moving it from 22 toward 28 reduces file size at the cost of some quality. For web video and social sharing, RF 24-26 is usually a good balance of file size and acceptable quality. For archival use, keep it at 18-20 for minimal quality loss.
For the broader picture of what different video formats and codecs mean for quality and compatibility, see our video formats guide and codec comparison. And if you need the source video first, MyVideoCity downloads from TikTok, Instagram, Facebook, X, and Vimeo directly.