WebM to MP4 Converter Online: Free, Private, No Upload
Convert WebM, MKV and MOV to MP4 in seconds. The conversion runs in your browser with FFmpeg, so your video is not uploaded to our servers. No watermark and no sign-up.
- No upload
- No sign-up
- H.264 MP4 output
- Free, no watermark
- Runs in your browser
- No upload
- Local FFmpeg
- No watermark
How to convert WebM to MP4 in 3 steps
- 1
Choose your video
Select a WebM, MKV or MOV file from your device.
- 2
Click Convert
The FFmpeg engine converts the file to an H.264 MP4 in your browser.
- 3
Download the MP4
Download your MP4 file. No watermark and no sign-up.
Why convert WebM to MP4?
WebM is an open format that is popular for web video and browser screen recordings. It is not supported everywhere. If you have tried to play a WebM file on an iPhone, import it into Adobe Premiere Pro, or upload it to Instagram, you have probably hit an error.
MP4 is the most widely supported video format. It usually uses H.264 video and AAC audio, which nearly every device, browser and editor can play. Converting WebM to MP4 makes your video work almost anywhere.
WebM vs MP4: what is the difference?
Both are video containers, but they are used differently and have different device support.
| WebM | MP4 | |
|---|---|---|
| Best known for | Web video and screen recordings | Playback on almost every device |
| Typical video codec | VP8 or VP9 | H.264 (AVC) |
| Typical audio codec | Vorbis or Opus | AAC |
| iPhone, iPad and QuickTime | Often not supported | Supported |
| Premiere Pro and Final Cut | Limited support | Supported |
| Social media uploads | Often rejected | Accepted almost everywhere |
Features of this free WebM to MP4 converter
FFmpeg in your browser
Uses WebAssembly-powered FFmpeg to process video on your own device. No server queue and no upload wait.
Plays everywhere
WebM files often fail on iPhone, QuickTime or Adobe Premiere. H.264 MP4 plays on nearly all devices and editors.
High-quality output
Re-encodes with H.264 at CRF 22, a common quality setting, so the MP4 looks very close to the original.
Audio kept
Audio is converted to standard AAC and stays in sync with the video.
No software to install
No VLC, HandBrake or desktop app. It works in a modern browser such as Chrome, Edge, Firefox or Safari.
Private by design
Your video is converted in your browser and is not uploaded to our servers.
When to convert WebM to MP4
Fix iPhone playback
WebM files often will not play on iPhone or in QuickTime. Converting to MP4 makes them compatible with Apple devices.
Edit in Premiere Pro or Final Cut
Editors handle MP4 much better than WebM. Convert first, then import the clip into your timeline.
Share on social media
Instagram, TikTok and WhatsApp work best with MP4. Converting helps your video upload without format errors.
Save screen recordings and clips
Browser screen recorders and chat apps often save WebM. Convert them to MP4 to email them or keep them in your library.
Browser converter vs typical online converters
Many online converters upload your file to a server, make you wait in a queue, or add a watermark. Here the work happens on your device.
| Feature | TToolDeck | Typical converters |
|---|---|---|
| No upload to a server | Yes | No |
| Free with no sign-up | Yes | Partial |
| No watermark on output | Yes | Partial |
| Runs entirely in your browser | Yes | No |
| No waiting in an upload queue | Yes | No |
| Your video stays on your device | Yes | No |
Comparison reflects general trends at the time of writing. Features of other tools may change.
WebM to MP4 FAQ
How do I convert WebM to MP4 for free?
Choose your WebM file in the tool above, click Convert, and download the MP4 when it finishes. It is free, needs no sign-up and adds no watermark.
What is a WebM to MP4 converter?
It is a tool that converts a WebM video into the MP4 format. MP4 with H.264 video and AAC audio is supported by almost every device, browser and video editor.
Why should I convert WebM to MP4?
WebM files often fail to play on Apple devices, in video editors such as Premiere Pro, and on some social media platforms. MP4 is the safer format for sharing and editing.
Does it upload my video to a server?
No. The conversion runs in your browser using WebAssembly (FFmpeg), so your video is not sent to our servers.
Can I convert WebM to MP4 without losing quality?
Converting always re-encodes the video, so it is not mathematically lossless. This tool uses H.264 at CRF 22, a high-quality setting, so the result looks very close to the original in normal viewing.
Which video formats are supported?
WebM, MKV and MOV files can be converted to MP4. For other formats, convert them to one of these first.
Is there a file size limit?
Files up to about 150 MB work best. There is no daily limit, but very large files can make your browser run out of memory.
Does it keep the audio?
Yes. The audio track is converted to AAC and kept with the video.
Why does the first conversion take longer?
The first time you use the tool, your browser downloads the FFmpeg engine. After that it is usually cached, so later conversions start faster.
Why will my WebM file not play on iPhone?
Many iPhones and QuickTime versions do not support the VP8 or VP9 codecs that WebM commonly uses. Converting to H.264 MP4 solves this.
Does it work on mobile?
Yes, in modern mobile browsers. For large videos a desktop computer is much faster.
Can I convert MKV or MOV to MP4 too?
Yes. The same tool converts MKV and MOV files to H.264 MP4.