The heavy encoding runs off your machine
Rebuilding VP8 or VP9 video as H.264 is heavy work. It runs on indox infrastructure, not on your own machine, so nothing is installed and a single recording needs no account. Files travel over HTTPS.
Free WEBM to MP4 converter
The WebM your browser recorded becomes an MP4 that iPhones, televisions and most editing software open.
Converting WebM to MP4 gives you a video that opens almost everywhere, including iPhones, older Safari versions, televisions and most editing software. The one thing to know is that this is a full re-encode: a VP8 or VP9 picture is rebuilt as H.264, so it takes longer than a simple rewrap and costs a small amount of quality.
Transfers use HTTPS, and files converted on the free tier are deleted within 24 hours, so the result is not a long-term archive. Quality depends on the source file, so open the MP4 file once before you share it.
FromWebMLossy
WebM (web media container based on Matroska)
An open, royalty-free video container built for the web and based on Matroska. It carries VP8, VP9 or AV1 video with Vorbis or Opus audio, and it is what browser screen recorders and many web downloads produce.
ToMP4Lossy
MP4 (MPEG-4 Part 14)
The most widely supported video container, standardised as MPEG-4 Part 14. Players, phones, televisions and editors generally expect it to hold H.264 or HEVC video with AAC audio, although the container can technically carry other codecs too.
A short 1280 × 720 clip with sound, saved as WEBM, converted on indox.org
- WEBMthe original
- 2.6 MB
- MP4from indox, 11% smaller
- 2.3 MB
Why use indox to convert WEBM to MP4?
A progress bar for long recordings
Because VP8 and VP9 frames are decoded and compressed again, an hour-long screen recording is a much longer job than a short clip. The progress bar tracks the job, and you can cancel and start over if you added the wrong take.
A share link for people on Apple devices
WebM playback is unreliable on iPhones and older Macs. When the MP4 is ready you can download it or share it with a link, so the person receiving it gets a file their device opens. On the free tier the file is deleted within 24 hours, so send the link promptly.
What happens to your video
Stays
- Your original WebM, which is not touched
- AV1 video, which MP4 can hold, so it is copied without re-encoding
- Audio, which is first copied as it is when the MP4 can hold it
Changes
- VP8 and VP9 video is decoded and encoded again as H.264, a second lossy pass
- Container: the clip is rewrapped as MP4 with the index moved to the start of the file, which helps playback
- If the MP4 cannot take the copied audio, the whole job is redone with H.264 video and AAC audio
How do I convert WEBM to MP4 online?
- 1
Add your WebM recording
Drag the WebM onto the box or choose it from your device; files in Dropbox, Google Drive or at a URL can be imported. Keep the original if it has a transparent background, which the MP4 will lose.
- 2
Confirm MP4 and start the re-encode
Once the output format shows MP4, start the conversion. Every frame is decoded and compressed again, so give a long screen recording time; the progress bar shows the job.
- 3
Download the MP4 and scrub the timeline
Open the downloaded MP4 and drag through the timeline to confirm that the duration shows and seeking works. In an editor, listen near the end for audio that has drifted out of sync.
What do I get from indox's WEBM to MP4 converter?
You get an MP4 in which a VP8 or VP9 picture has been rebuilt as H.264, the format QuickTime, iMovie, Premiere Pro and PowerPoint expect, while AV1 video and the audio are copied across when the MP4 can hold them. The re-encode costs a small amount of quality, and the MP4 is often somewhat larger than the WebM. No software is installed, and a single recording needs no account.
- VP8 and VP9 video rebuilt as H.264 in a standard MP4
- A complete file with a proper seek index
- Plays in QuickTime, iMovie, Premiere Pro and PowerPoint
- A share link for people on an iPhone or older Mac
- Recordings on the free tier are deleted within 24 hours
What are the limits for WEBM to MP4?
Size
The upload box shows the live size limit before you add a file. Signing in raises it, and paid plans raise it further.
Formats
WEBM in, MP4 out. Pick another output on the converter if you need a different format.
Privacy
Files are encrypted in transit over HTTPS and processed on indox infrastructure.
Deletion
Free-tier files are deleted automatically within 24 hours after the job finishes.
Limits worth knowing
- Quality cannot improve. Re-encoding a lossy video with another lossy codec always loses a little, and heavy compression in the source stays visible.
- Transparency is lost. WebM with VP8 or VP9 can carry an alpha channel, but the H.264 video normally used in MP4 cannot, so clear areas become solid.
- Screen recordings often have a variable frame rate. Depending on the source, that can show up as audio drifting out of sync in some editors.
- Long or high-resolution recordings take noticeably longer than audio or image conversions, because video re-encoding is heavy work.
When the result is not what you expected
| What you see | Why | What to do |
|---|---|---|
| The MP4 still does not play on an older device | A WebM that holds AV1 video is not re-encoded, so the MP4 holds AV1 rather than H.264 | Play it in a current browser or desktop player, or export the clip from its source as VP8 or VP9 and convert again |
| The conversion takes much longer than a simple rewrap | VP8 and VP9 video is decoded and encoded again, frame by frame | Give long recordings time, and cancel if you added the wrong file |
| The picture is a little softer than the WebM | Re-encoding to H.264 is a second lossy pass over the video | Keep the WebM as your master and use the MP4 only where WebM is refused |
What do the free and paid plans add?
Free
- All converters
- Daily credit refresh
- Email support
Basic
- Access to all features
- AI Extract
- Priority conversions
- Email support
Highest priority
Premium
- Everything in Basic
- Highest priority queue
- Larger file limits
- Priority support
Pay-As-You-Go
- No subscription
- Credits never expire
- Opt-in auto-refill
- Access to all features
Which conversions are close to WEBM to MP4?
AVI to MP4
Older video files at a smaller size
MOV to MP4
iPhone and Mac video that plays anywhere
MKV to MP4
Video for phones, TVs and editors
MP4 to MP3
The sound from a video
Related conversionsReverseMP4 to WEBM
WebM vs MP4: what is the difference?
| Compared on | WebM | MP4 |
|---|---|---|
| What it is | An open, royalty-free media file format designed for the web | The MPEG-4 file format, ISO/IEC 14496-14 |
| Video codecs | VP8 or VP9, as the WebM project describes it | Commonly AVC (H.264) and HEVC; AV1 also fits in MP4 |
| Audio codecs | Vorbis or Opus | AAC is among the listed subtypes |
| Intended use | Video on the web | Web and other online applications, mobile devices and broadcasting |
Who can use a WEBM to MP4 converter?
When to use it
- Opening a browser screen recording in iMovie, Final Cut Pro or Premiere Pro, which commonly reject WebM on import.
- Sending a clip to someone on an iPhone or an older Mac where WebM playback is unreliable.
- Uploading a video to a social platform, learning system or slide deck that accepts MP4 files only.
- Playing a downloaded web video on a television, games console or car screen from a USB stick.
Where can I read more about converting files?
Sources
- About WebMThe WebM Project
- MPEG-4 File Format, Version 2 (ISO/IEC 14496-14)Library of Congress
- Web video codec guideMDN Web Docs
- FFmpeg Formats Documentation: mp3 muxerFFmpeg
Facts checked on October 16, 2026
Do it all with indox
No tool matches that search.
WEBM to MP4 FAQs
Does converting WebM to MP4 lose quality?
Yes, slightly. Both formats use lossy video codecs, and moving from VP8 or VP9 to H.264 means decoding the picture and compressing it again, which discards a little more detail. On a clean source the difference is usually hard to see. On a recording that was already heavily compressed, blockiness and banding can become more noticeable.
Can I just rename .webm to .mp4?
No. Renaming changes the label, not the contents, so the file is still a WebM container holding VP9 and Opus streams. A forgiving player such as VLC may open it anyway by inspecting the data, but an iPhone, iMovie or a strict uploader will still reject it. The streams have to be re-encoded and written into a real MP4 structure.
Why won't my WebM file play on iPhone or in Safari?
Because Apple was late to support the codecs WebM uses. Older versions of iOS and Safari cannot decode VP8 or VP9 at all, and newer ones support them only partly, with behaviour that varies by version and device. The Photos app, iMovie and QuickTime Player expect H.264 or HEVC in an MP4 or MOV file instead.
Why is the MP4 bigger than the WebM?
Usually because H.264 needs more data than VP9 to reach the same visual quality. VP9 is noticeably more efficient, so matching the look of the source produces a larger file. The opposite also happens: a WebM recorded at a generous bitrate can shrink once it is re-encoded.
Why does my WebM screen recording show no duration or refuse to seek?
WebM files written live by a browser recorder often lack a stored duration and a seek index, because the recorder streams data out before it knows how long the clip will be. Players then show a blank timeline or cannot skip ahead. Converting writes a complete MP4 with a proper index, which usually fixes both problems.
Will a transparent WebM stay transparent as MP4?
No. Transparent WebM clips store an alpha channel alongside VP8 or VP9 video, and standard H.264 in MP4 has nowhere to keep it. The transparent regions are filled with a solid colour. If you need transparency for overlays or animated stickers, keep the WebM, or use a format designed for alpha such as ProRes 4444 in MOV.