Free WEBM Converter: No Sign-up, Files Never Uploaded
This free WEBM converter runs entirely on your device. You do not need an account or a login, and your files are never uploaded, so they never leave your browser.
WebM in short. Open, royalty-free format from Google, usually VP9 or AV1 video with Opus audio. Plays in all major browsers. Can carry an alpha channel with VP9.
From WEBM you can convert to MP4, MOV, MKV, AVI, WMV and FLV, and 19 more formats. Some of these pairs can need a one-time engine download, which the page announces before it starts.
- Free
- No sign-up
- Never uploaded
- No watermark
Your files are converted on your device and never uploaded.
How to convert
- Add your WEBM files by dragging them onto the converter or by using the file picker.
- Choose the format you want from the list of targets that fit your file.
- Open the options if you want to change quality or size, or keep the defaults.
- Press Convert and watch the progress shown for each file.
- Download each result, or take them all together as one ZIP when you converted several files.
Features
- Reads .webm files and can also write them.
- Free, with no watermark added to the result.
- No sign-up and no login.
- Your files are never uploaded and never leave your device.
- Batch conversion with a ZIP download for several results.
- The input is recognised by its content, not only by its file name.
- 25 target formats to choose from.
- WEBM supports transparency, and the converter keeps it where the target can.
- A one-time engine download is cached by your browser.
Supported formats
| Format | Read | Write | Notes |
|---|---|---|---|
| GIF.gif | Yes | Yes | Limited to 256 colours per frame, with single-bit transparency. |
| MP4.mp4 | Yes | Yes | The most widely supported video format: plays on phones, browsers, TVs and editors. |
| WebM.webm | Yes | Yes | Open, royalty-free format from Google, usually VP9 or AV1 video with Opus audio. |
| MOV.mov | Yes | Yes | Apple’s QuickTime container, the default for iPhone and Mac screen recordings. |
| MKV.mkv | Yes | Yes | Matroska: an open container that holds any number of video, audio and subtitle tracks. |
| AVI.avi | Yes | Yes | Audio Video Interleave: a container Microsoft introduced in 1992. |
| WMV.wmv | Yes | Yes | Windows Media Video, Microsoft’s format from the early 2000s. |
| FLV.flv | Yes | Yes | Flash Video, the standard for web video in the Adobe Flash era. |
| F4V.f4v | Yes | No | F4V is an obsolete Flash format that is read only here; convert it to MP4. |
| 3GP.3gp | Yes | Yes | Small-file video container defined by 3GPP for early mobile phones. |
| OGV.ogv | Yes | Yes | Ogg video, usually Theora video with Vorbis audio. |
| MPEG.mpeg | Yes | Yes | MPEG-1 or MPEG-2 program stream, the format behind Video CDs and DVDs. |
| MPEG-TS.ts | Yes | Yes | MPEG transport stream, used in broadcast TV, Blu-ray and HLS streaming. |
| VOB.vob | Yes | No | VOB files come from DVD discs and are read only; convert them to MP4. |
| M4V.m4v | Yes | No | M4V is an MP4 variant; convert it to MP4, which every device plays. |
| ASF.asf | Yes | No | ASF is read only here; WMV is the video format that can be created. |
About the formats
About WEBM
Open, royalty-free format from Google, usually VP9 or AV1 video with Opus audio.
Plays in all major browsers.
Can carry an alpha channel with VP9.
WEBM uses lossy compression. It supports transparency.
What WEBM can become
WEBM to MP4 runs in the page.
WEBM to MOV runs in the page.
WEBM to MKV runs in the page.
WEBM to AVI can need a one-time download of about 31 MB.
WEBM to WMV can need a one-time download of about 31 MB.
WEBM to FLV can need a one-time download of about 31 MB.
WEBM to 3GP can need a one-time download of about 31 MB.
WEBM to OGV can need a one-time download of about 31 MB.
Converting to WEBM
Pages for converting to WEBM start from MP4, MOV, MKV, AVI and OGV.
Privacy: how it works
- Your WEBM files stay on your device. The page reads each file with the browser's file API, converts it with code running in the tab, and hands the result back as a download. No upload happens, so there is no copy of your file on our servers to protect, delete or leak.
- There is nothing to sign up for and no login. The converter does not ask for an email address, and it does not need to know who you are to do its job.
- Some conversions use a WebAssembly engine that your browser downloads once, the first time you need it. Only the engine is fetched, never your file, and the page shows the approximate size before it starts. Your browser caches it, so later conversions skip the download.
- You can check the claim yourself: open your browser developer tools, watch the Network tab while a file converts, and you will see no request that carries your file.
Tips
- Try a short clip first to check quality and size before you convert a long video.
- Keep the original resolution unless you need a smaller file; shrinking the frame is the quickest way to cut size.
- Close other heavy tabs while converting, because the work uses your own memory and processor.
- Convert one large file at a time on a phone or a low-memory computer.
- WEBM is lossy, so convert from the original when you can instead of from a copy.
Frequently asked questions
Is it really free?
Yes. There is no price, no trial, no credit card and no watermark added to your results. Ulkaa Tool does the conversion with your own device, so there is no server bill to pass on to you.
Are my files uploaded?
No. Your WEBM files are read and converted inside your browser and are never sent to Ulkaa or to anyone else. The result is created on your device and you save it from there. Some conversions load a small conversion engine the first time you use them. That download is the only network traffic, it contains no file of yours, and your browser keeps it for next time.
Do I need an account?
No. There is no sign-up and no login. Open the page, add your files and convert. An Ulkaa account is not needed for anything on this tool.
Is there a file size limit?
No limit is set by us. The real limit is your device: the conversion uses your own memory and processor, so very large files can be slow or fail on a weak phone or an older computer. Close other heavy tabs and convert WEBM files one at a time if a big batch struggles.
What can I convert WEBM files to?
You can convert WEBM to MP4, MOV, MKV, AVI, WMV, FLV, 3GP, OGV, MPEG, TS, GIF, WEBP, MP3, WAV, OGG, Opus, AAC, M4A, M4R, FLAC, ALAC, WEBA, AIFF, AC3 and AMR. Pick one on the converter and it applies to every file you add.
Can I convert other files to WEBM?
Yes. MP4, MOV, MKV, AVI and OGV can be converted to WEBM.
Can I convert many WEBM files at once?
Yes. Add as many files as your device can handle. Each one is converted on its own and you can download them one by one or as a single ZIP.
Is WEBM lossy?
Yes. WEBM saves space by discarding some detail, so converting from WEBM cannot restore what was lost and converting to it loses a little.
Does WEBM keep transparency?
Yes, WEBM can store transparency. If you convert to a format that cannot, see-through areas are flattened onto a solid background.