Convert WebM to MP4 with an API

Convert WebM to MP4 directly in the live demo below, or use the same Assembly Instructions to transcode uploaded videos automatically. 🤖/video/encode applies the web/mp4 preset so the output uses broadly compatible MP4 settings.

WebM commonly contains VP8, VP9, or AV1 video with Opus or Vorbis audio. MP4 is a container rather than a codec, and broad compatibility usually means H.264 video with AAC audio. Changing those codecs requires transcoding, so the result may not be bit-for-bit identical and processing time depends on the source duration, dimensions, and codec.

Use MP4 when playback compatibility across browsers, mobile devices, editing tools, and social platforms matters. Keep WebM when its modern codecs and web-focused delivery are a better fit. Production workflows can add resolution, bitrate, thumbnail, and storage Steps to the same pipeline.

Step 1:

Handle uploads

We can handle uploads of your users directly.Learn more

surf.webm

Video – 2.3 MB

22s · 1280 × 720

":original": {
  "robot": "/upload/handle"
}

/upload/handle

This bot receives uploads that your users throw at you from browser or apps, or that you throw at us programmatically

Step 2:

Transcode, resize, or watermark videos

We offer a variety of video encoding features like optimizing for different devices, merging, injecting ads, changing audio tracks, or adding company logos.Learn more

surf.mp4

Video – 5.5 MB

22s · 1280 × 720

"converted": {
  "use": ":original",
  "robot": "/video/encode",
  "result": true,
  "ffmpeg_stack": "v7",
  "preset": "web/mp4/720p",
  "turbo": false
}

/video/encode

This bot encodes, resizes, applies watermarks to videos and animated GIFs

Step 3:

Export files to Amazon S3

We export to the storage platform of your choice.Learn more

:original

https://demos.transloadit.com/6f/f32343e0c5463996b7c2fecd386251/surf.webm

converted

https://demos.transloadit.com/74/488513d48a49fdbf0c9de7e19cf1d0/surf.mp4

"exported": {
  "use": [
    "converted",
    ":original"
  ],
  "robot": "/s3/store",
  "credentials": "demo_s3_credentials",
  "url_prefix": "https://demos.transloadit.com/"
}

/s3/store

This bot exports encoding results to Amazon S3

Live Demo. See for yourself

Loading Uppy demo…

This live demo is powered by Uppy, our open source file uploader that you can also use without Transloadit, and tus, our open protocol for resumable file uploads that is making uploading more reliable across the world.

Build this in your own language

<!-- This pulls Uppy from our CDN -->
<!-- For smaller self-hosted bundles, install Uppy and plugins manually: -->
<!-- npm i --save @uppy/core @uppy/dashboard @uppy/remote-sources @uppy/transloadit ... -->
<link
  href="https://releases.transloadit.com/uppy/v3.10.0/uppy.min.css"
  rel="stylesheet"
/>
<button id="browse">Select Files</button>
<script type="module">
  import {
    Uppy,
    Dashboard,
    ImageEditor,
    RemoteSources,
    Transloadit,
  } from 'https://releases.transloadit.com/uppy/v3.10.0/uppy.min.mjs'
  const uppy = new Uppy()
    .use(Transloadit, {
      waitForEncoding: true,
      alwaysRunAssembly: true,
      assemblyOptions: {
        params: {
          // It's often better store encoding instructions in your account
          // and use a `template_id` instead of adding these steps inline
          steps: {
            ':original': {
              robot: '/upload/handle',
            },
            converted: {
              use: ':original',
              robot: '/video/encode',
              result: true,
              ffmpeg_stack: 'v7',
              preset: 'web/mp4/720p',
              turbo: false,
            },
            exported: {
              use: ['converted', ':original'],
              robot: '/s3/store',
              credentials: 'demo_s3_credentials',
              url_prefix: 'https://demos.transloadit.com/',
            },
          },
        },
      },
    })
    .use(Dashboard, { trigger: '#browse' })
    .use(ImageEditor, { target: Dashboard })
    .use(RemoteSources, {
      companionUrl: 'https://api2.transloadit.com/companion',
    })
    .on('complete', ({ transloadit }) => {
      // Due to `waitForEncoding:true` this is fired after encoding is done.
      // Alternatively, set `waitForEncoding` to `false` and provide a `notify_url`
      console.log(transloadit) // Array of Assembly Statuses
      for (const assembly of transloadit) {
        console.log(assembly.results) // Array of all encoding results
      }
    })
    .on('error', (error) => {
      console.error(error)
    })
</script>

Read docs: Browsers

So many ways to integrate

Transloadit is a service for companies with developers. And there are many ways developers can put Transloadit to good use inside your company to automate media processing.