WebM to MP4 Converter
Convert WebM to MP4 so screen recordings, browser captures and PS5 clips play on iPhone, in WhatsApp and in Windows editors. ProMedia re-encodes the VP8, VP9 or AV1 video to H.264 and the Opus audio to AAC, the MP4 flavour every device accepts, using your device’s hardware encoder where the browser offers one. Nothing is uploaded and there is no size cap.
- Runs on your device
- WebCodecs · GPU
- FFmpeg
- Works offline
Updated
Drop your videos here
How to convert WebM to MP4
Step 1: Drop your WebM files on the box above: browser screen recordings, game clips or downloads.
Step 2: Keep Quality on Balanced. Choose Best quality for footage you will edit, Faster for a quick share.
Step 3: Press Convert. The video becomes H.264 and the audio AAC.
Step 4: Download the MP4 files, or all of them as one ZIP.
Good to know
Settings explained
- Quality
- Only used when a stream has to be re-encoded. Compatible streams are copied with no quality loss.
- Faster: Smaller file, quickest export
- Balanced: Good quality at a sensible size
- Best quality: Largest file, slowest export
- Video codec
- Automatic copies the original video stream when the new format can hold it, so there is no quality loss.
- Automatic: Best codec the format and your device support
- H.264 (AVC): Plays everywhere
- H.265 (HEVC): About 35% smaller, newer devices
- VP9: Web / WebM
- AV1: Smallest files, slowest to encode
- Always re-encode
- Off: compatible streams are copied instantly and losslessly. On: every stream is re-encoded, which can fix playback glitches.
Formats
Batch-friendly: add many files and they are processed one after another — if one fails, the rest still finish.
How it runs
- Hardware video engine
- Video is decoded and encoded by your device’s media hardware through WebCodecs — usually several times faster than real time.
- FFmpeg (when needed)
- Older formats and a few filters use FFmpeg compiled to WebAssembly. It downloads once (about 31 MB) the first time it is needed and is cached for offline use.
WebM vs MP4: is WebM better?
WebM is better on web pages: VP9 and AV1 fit more picture into fewer bits, and the format is royalty-free. MP4 with H.264 is better almost everywhere else, because phones, TVs, messaging apps and editors expect it. That is why this page re-encodes instead of only re-wrapping.
| Feature | WebM | MP4 (H.264 + AAC) |
|---|---|---|
| Video codecs | VP8, VP9, AV1 | H.264 (MP4 can also hold HEVC and AV1) |
| Audio codecs | Opus, Vorbis | AAC |
| Bits for the same picture | VP9 about 35% fewer than H.264 | Baseline |
| Where the files come from | Browser screen and camera recorders, PS5 captures, web downloads | Phones, cameras, editing apps |
| iPhone Photos app and iMovie | Not accepted | Accepted |
| Best for | Embedding on websites | Sharing, editing and messaging |
What is a WebM file?
A WebM file is an open video format backed by Google, built on the Matroska container but limited to royalty-free codecs: VP8, VP9 or AV1 video with Opus or Vorbis audio. Web apps that record your screen or camera in Chrome usually save WebM, and the PS5 saves game clips as WebM unless you change its capture format to MP4.
The trouble starts outside the browser. The iPhone Photos app, many smart TVs, WhatsApp and most editing software expect MP4.
Does converting WebM to MP4 reduce quality?
Slightly, because the video is decoded and compressed again as H.264. The bitrate is set from what the source spends, scaled up because H.264 needs more bits than VP9 for the same detail, so at Balanced the difference is hard to see on screen recordings and gameplay.
For a lossless result, open Advanced settings and set Video codec to Automatic. The VP9 or AV1 stream is then copied into the MP4 unchanged, but many players, older iPhones included, will not open it.
| Setting | Video in the MP4 | Plays everywhere? | Quality |
|---|---|---|---|
| Default (H.264 + AAC) | Re-encoded to H.264 | Yes | Very close to the original |
| Quality: Best | H.264 with up to 2× the codec-adjusted source bitrate | Yes | Closest to the original; bigger file |
| Video codec: Automatic | VP9, VP8 or AV1 copied as-is | Browsers and recent devices only | Identical |
| Resolution: 720p | Downscaled H.264 | Yes | Softer, much smaller |
Can you rename WebM to MP4?
No. Renaming changes the label, not the contents: the file is still WebM with VP8 or VP9 video and Opus audio, so iPhones, WhatsApp and editors either refuse it or play it without sound. A real conversion writes a new MP4 container with codecs those apps understand.
Convert WebM to MP4 on iPhone, Mac, Windows or Android
iPhone and iPad
In Safari, tap the drop zone and pick the WebM from the Files app, where downloads and AirDropped files land. Save the MP4, then share it to Photos to keep it in your camera roll.
Mac
Drag the WebM files from Finder into Safari or Chrome. The MP4 opens in QuickTime Player and imports into iMovie and Final Cut Pro.
Windows
Drag the files into Chrome or Edge. On most PCs the H.264 encode runs on the graphics card, so a few minutes of recording convert quickly.
Android
Open the page in Chrome, tap the drop zone and choose the WebM from Downloads. The MP4 is saved back to Downloads, ready to send in WhatsApp.
Tips & troubleshooting
Recording has no length or will not seek? Browser recordings often lack an index. Converting writes a fresh MP4 index; if it still misbehaves, try repair video.
Recording your screen in the first place? The screen recorder saves MP4 directly, so there is nothing to convert afterwards.
Over WhatsApp’s size limit after converting? Run the MP4 through compress video for WhatsApp.
Long 4K game clip? Set Resolution to 1080p or 720p under Advanced settings for a far smaller MP4.
Making a WebM for your own website instead? Use MP4 to WebM.
WebM to MP4 Converter FAQ
How do I convert WebM to MP4 without losing quality?
Open Advanced settings and set Video codec to Automatic. The VP9, VP8 or AV1 stream is then copied into the MP4 bit for bit, which is almost instant. The trade-off is compatibility: iPhones, many TVs and editors cannot play VP9 in MP4, so the default H.264 re-encode is safer for sharing.
Can you watch WebM on iPhone?
Sometimes in a recent version of Safari, but not in the Photos app, iMovie or most other apps. Converting to MP4 with H.264 makes the clip play everywhere on the iPhone and lets you save it to the camera roll.
Does WhatsApp support WebM?
WhatsApp expects MP4 for video messages. A WebM may only go through as a document that the other person has to download and open elsewhere. Convert it to MP4 here first and it sends and plays like any other video.
How do I convert WebM to MP4 on Mac?
Open this page in Safari or Chrome, drag the WebM files onto the drop zone and press Convert. The MP4s are saved to Downloads and open in QuickTime Player, Photos and iMovie. Nothing is uploaded.
Why does WebM need re-encoding when MKV usually does not?
MKV files usually contain H.264 or HEVC, which MP4 players already understand, so those streams can be copied. WebM always uses VP8, VP9 or AV1 with Opus or Vorbis audio, which many MP4 players do not support, so the video becomes H.264 and the audio AAC.
Is your recording uploaded anywhere?
No. Your recording is processed by your own browser on your own device. There is no server that receives files, so nothing is uploaded, stored or shared. You can even switch to airplane mode once the page has loaded.