How to Convert WebM to MP4 with VLC [Full Guide + Fixes]

Got a .webm file that won't play on your phone, TV, or video editor? You're not alone. WebM is a video format developed by Google's WebM Project for the web — it's lightweight and works great in browsers, but plenty of devices and apps still don't support it. MP4, on the other hand, plays pretty much everywhere.

The good news: VLC media player can handle this conversion for free. The less-good news: VLC's converter has a few well-known quirks — missing audio, weird file extensions on Mac, and painfully slow speeds. This guide covers everything: the full VLC conversion process for both Windows and Mac, fixes for when things go wrong, and a faster alternative if VLC isn't cutting it.

Method 1 — Convert WebM to MP4 Using VLC (Windows & Mac)

VLC's built-in converter works for basic WebM-to-MP4 jobs. The process is slightly different on Windows and Mac, so here are the steps for both.

On Windows

1. Step 1: Open VLC and go to Media → Convert/Save (or press Ctrl+R to get there directly).
2. Step 2: Click the Add button, browse to your .webm file, select it, and click Open. Then click the Convert/Save button at the bottom.
3. Step 3: In the Convert window, find the Profile dropdown. Select Video - H.264 + MP3 (MP4). This is the setting that tells VLC to output an MP4 file with H.264 video and MP3 audio.
4. Step 4: Click Browse next to the Destination field. Pick a folder, type in a filename, and make sure it ends with .mp4 — VLC won't add the extension for you.
5. Step 5: Click Start. You'll see VLC's progress bar move across the bottom. When it finishes, your new MP4 file will be in the destination folder.

Tip: If the progress bar seems stuck at the beginning, give it a minute. VLC can be slow to start, especially with large files.

On Mac

The Mac version of VLC uses a slightly different workflow — and has one quirk you need to know about.

1. Step 1: Open VLC and go to File → Convert/Stream (not Media — that menu doesn't exist on macOS).
2. Step 2: In the Convert & Stream window, drag and drop your .webm file into the "Drop media here" area. Or click Open media to browse for it.
3. Step 3: Under Choose Profile, VLC should auto-select Video - H.264 + MP3 (MP4). If it doesn't, pick it from the dropdown.
4. Step 4: Click Save as File, then click Browse to choose where to save the output.
5. Step 5: Here's the catch — VLC on Mac defaults to saving with an .m4v extension instead of .mp4. Either type your filename ending with .mp4 in the save dialog, or just rename the file afterward. The actual contents are the same; only the extension differs.
6. Step 6: Click Go! and wait for the conversion to complete.

VLC WebM to MP4 Not Working? Common Issues & Fixes

VLC's converter gets the job done for basic conversions, but it breaks in predictable ways. Here are the four most common issues and how to solve each one.

Fix 1 — No Audio After Conversion

This is hands down the most reported problem with VLC WebM conversion. You follow all the steps, the video converts fine, but when you play the MP4 — silence. The video plays, but there's no sound at all.

Why it happens: Most WebM files use the Opus audio codec. When VLC converts to MP4, it needs to transcode that Opus audio into AAC or MP3. Sometimes VLC's default settings don't handle this correctly, and the audio track just gets dropped.

How to fix it:

1. Before starting the conversion, click the wrench icon (or Customize) next to the Profile dropdown
2. Go to the Audio codec tab
3. Make sure the Audio checkbox is ticked
4. Set the Codec to MPEG Audio or AAC
5. Change the Sample Rate to 48000 Hz
6. Click Save

If that doesn't work, try one more thing: uncheck "Keep original audio track" in the same settings. This forces VLC to transcode the audio instead of trying to copy it directly.

Fix 2 — Output Saved as .m4v Instead of .mp4 (Mac)

You converted your file on Mac, everything seemed fine, but the output has an .m4v extension instead of .mp4.

Why it happens: VLC on macOS defaults to the .m4v container, which is essentially Apple's version of .mp4. The contents are identical — same H.264 video, same audio codec, same container structure.

How to fix it: Just rename the file. Change the extension from .m4v to .mp4. That's it. No re-conversion needed, no quality loss. The file is already an MP4 in everything but name.

Fix 3 — Conversion Is Extremely Slow

Noticed that converting a 20-minute WebM file takes... roughly 20 minutes? That's not a bug — that's how VLC works.

Why it happens: VLC converts at approximately real-time speed. It doesn't use GPU acceleration, so your graphics card sits idle while your CPU does all the heavy lifting. For short clips, this is fine. For a 2-hour webinar recording, you'll be waiting a while.

Workaround: There's no setting in VLC that meaningfully speeds this up. If you regularly convert large files or need to batch-process multiple WebM files, you'll want a dedicated converter that supports GPU acceleration. (More on that in Method 2 below.)

Fix 4 — Video Is Corrupted or Won't Play After Conversion

The conversion finishes, but the output MP4 is glitchy, won't play, or crashes your media player.

Why it happens: This typically occurs when the source WebM uses the VP9 or AV1 video codec. Older versions of VLC can struggle with these newer codecs during conversion, producing corrupted output.

How to fix it:

1. Update VLC to the latest version from videolan.org. Newer releases have much better VP9/AV1 support.
2. If updating doesn't help, try changing the output video codec: go to Profile settings → Video codec tab → change Codec to H.265 instead of H.264. Some VP9 sources convert more cleanly to H.265.
3. If the file still won't convert properly in VLC, the source file may need a more capable converter.

Method 2 — A Faster Way to Convert WebM to MP4 (UniFab Video Converter)

If VLC keeps giving you headaches — no audio, glacial speeds, or corrupted output — it might be time to try a tool that's actually designed for video conversion.

UniFab Video Converter is a free video converter that supports over 1,000 formats, including WebM to MP4. The key differences from VLC: it uses GPU acceleration (NVIDIA CUDA), handles batch conversion, and doesn't have VLC's audio issues with Opus-encoded WebM files.

How to convert WebM to MP4 with UniFab

Why consider UniFab over VLC for this task:

• Speed: GPU-accelerated conversion runs significantly faster than VLC's CPU-only approach
• Reliability: Proper Opus → AAC audio transcoding means no more missing audio
• Batch processing: Convert dozens of WebM files at once instead of one-by-one
• Quality preservation: Maintains original video quality during conversion
• Free to use: The free version covers basic conversion needs, and there's a 30-day trial with full features and no watermark

VLC vs. UniFab vs. Online Tools — Quick Comparison

Not sure which tool fits your situation? Here's how they stack up:

The quick verdict: Use VLC if you need a one-off conversion and don't mind waiting. Go with UniFab Video Converter for multiple files, large files, or when VLC's audio issues frustrate you. Online tools like CloudConvert work well for small files when you can't install anything — just keep in mind most have file size limits.

FAQ about WebM to MP4 Conversion

Can VLC convert WebM to MP4?

Yes. Open VLC, go to Media → Convert/Save (Windows) or File → Convert/Stream (Mac), add your WebM file, select the "Video - H.264 + MP3 (MP4)" profile, and click Start. It works for most basic conversions.

Why is there no audio after converting WebM to MP4 in VLC?

WebM files typically use the Opus audio codec, and VLC sometimes fails to transcode it properly. To fix this, click the wrench icon next to the profile, go to the Audio codec tab, set the sample rate to 48000 Hz, and make sure the Audio checkbox is enabled.

Is WebM better than MP4?

It depends on the use case. WebM files are generally smaller and optimized for web playback — it's an open format developed by Google. MP4 is universally compatible across devices, editors, and platforms. If you need to share, edit, or play video outside a web browser, MP4 is the safer choice.

How long does VLC take to convert WebM to MP4?

Roughly real-time. A 10-minute WebM video takes about 10 minutes to convert in VLC because it doesn't use GPU acceleration. For faster results, a GPU-accelerated converter can cut that time down significantly.

Can I batch convert multiple WebM files to MP4?

VLC technically supports batch conversion through its command-line interface, but the setup isn't beginner-friendly. If you need to convert multiple files at once, a free video converter with built-in batch support makes the process much simpler.

Does converting WebM to MP4 lose quality?

There's always some quality change when transcoding from one codec to another (VP9 → H.264). The loss is usually minimal and not noticeable in most cases. To minimize it, use a high bitrate setting in your converter, or use a tool that preserves quality during the transcoding process.

Why does VLC save as .m4v instead of .mp4 on Mac?

VLC on macOS defaults to the .m4v file extension, which is Apple's variant of the MP4 container. The file contents are identical to .mp4. You can simply rename the .m4v file to .mp4 — no conversion needed, no quality impact.

Can I convert WebM to MP4 online for free?

Yes. Services like CloudConvert and FreeConvert let you convert WebM files to MP4 directly in your browser. The tradeoffs: most limit file sizes to around 1 GB, conversion speed depends on your upload bandwidth, and you're sending your video to a third-party server.

What is the WebM format?

WebM is an open, royalty-free video format developed by Google through the WebM Project. It typically uses VP8 or VP9 video codecs with Vorbis or Opus audio. It's widely used for web-based videos, screen recordings, and files from browser-based tools like GoToMeeting and Loom.

Is VLC the best free WebM to MP4 converter?

VLC is a solid free option, but it has limitations for this task — particularly slow speed and recurring audio issues with WebM files. Dedicated converters that offer GPU acceleration and proper codec handling tend to produce more reliable results while being significantly faster.

How do I convert WebM to MP4 without losing quality?

Use a converter that supports high-bitrate H.264 encoding and doesn't re-compress unnecessarily. Set the output bitrate to match or exceed the source file's bitrate. Tools with quality-preservation modes will handle this automatically.

Can I convert WebM to MP4 on my phone?

VLC's mobile app doesn't include a conversion feature. Your best options are either an online converter (works in your phone's browser) or a dedicated mobile video converter app from the App Store or Google Play.

VLC handles basic WebM-to-MP4 conversion, and with the troubleshooting fixes above, you can work around most of its common issues. For anything beyond a quick one-off job — batch conversions, large files, or when you just don't want to deal with audio problems — UniFab Video Converter picks up where VLC leaves off. The free version covers most conversion needs, and the 30-day trial gives you access to every feature without watermarks.