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ASF to MKV Converter

Convert ASF to MKV online for free. Fast, secure, and high-quality conversion with no sign-up or software required.

Free to useNo file stored beyond 1 hourEncrypted over TLS 1.2/1.3No watermarks

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How it works

Three steps to your converted file

Everything happens in your browser tab - upload, pick a format, download. The heavy lifting runs on our servers.

01

Upload your file

Drag and drop, click to browse, or paste a URL. Batches take up to 20 files at once - 230+ input formats across video, audio, image, document, and archive types.

02

Choose an output format

Pick from over a hundred output formats. Filter by category or search by name - every option is open to everyone, no account needed.

03

Convert & download

Hit Convert and grab your download link moments later. Originals are erased when the job completes; results are cleared within about an hour.

What is an ASF file?

The Advanced Systems Format (ASF) is a proprietary digital audio and digital video container developed by Microsoft, serving as part of the Windows Media framework. It is designed for streaming media and uses a GUID-based object structure (Header, Data, and Index objects) to organize streams. ASF files typically contain Windows Media Audio (WMA) and Windows Media Video (WMV) codecs, though the container is codec-agnostic. The format supports Digital Rights Management (DRM) and extensible metadata via the Content Description Object.

How to open an ASF file

As a Microsoft-proprietary format, ASF files are natively supported on Windows operating systems via Windows Media Player and the Movies & TV app. macOS users generally cannot open ASF files without third-party components like Flip4Mac (discontinued) or universal players. The most reliable cross-platform solution for playing ASF containers without codec errors is the VLC media player, which supports the underlying WMA and WMV streams independently of the OS framework.

ASF Technical Info

Full Name
Advanced Systems Format
Developed By
Microsoft
Initial Release
1996
MIME Type
video/x-ms-asf

What is an MKV file?

The Matroska Video (MKV) file is an open-standard, free container format capable of holding an unlimited number of video, audio, picture, or subtitle tracks in one file. Unlike proprietary containers, Matroska is structured upon Extensible Binary Meta Language (EBML), allowing for significant flexibility and forward compatibility. It supports a vast array of codecs, including H.264, VP9, HEVC, AAC, Vorbis, and FLAC, and is particularly noted for its support of soft subtitles (SSA/ASS) and chapter entries, making it a standard for high-definition video distribution (HD) and anime fansubs.

How to open an MKV file

Native support for MKV is available in Windows 10/11 via the Movies & TV app and generally on Linux distributions. macOS requires third-party software, as QuickTime Player does not natively parse the Matroska container. The industry-standard solution for all operating systems is VLC Media Player, which includes built-in libraries for decoding the diverse codecs often encapsulated within MKV files. Alternative options include MPV and MPC-HC (Windows).

MKV Technical Info

Full Name
Matroska Video Container
Developed By
Matroska (non-profit)
Initial Release
2002
MIME Type
video/x-matroska

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Why RunConvert

The fastest way to convert any file

Purpose-built for speed, privacy, and breadth of format support.

Convert ASF to MKV in seconds

Every ASF to MKV conversion runs on our servers, so your device stays fast and the output quality stays intact.

Fast, cloud-powered

No queue, no waiting. Files are processed on high-performance servers and returned in seconds, even for large files.

Secure & private

Encrypted in transit and never shared with anyone. Uploads are erased the moment your job completes, and results shortly after.

Free - no account needed

Convert without creating an account - no credit card, no trial clock. Sign in only if you want history and higher daily limits.

Developer API

Convert ASF to MKV via API

Automate ASF to MKV conversions in three steps: create a job, upload your file, then poll for the result.

# 1. Create job
curl -X POST https://api.runconvert.com/v3/jobs \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "tag": "asf-to-mkv",
    "tasks": {
      "upload-file": {
        "operation": "import/upload"
      },
      "convert": {
        "operation": "convert",
        "input": "upload-file",
        "output_format": "mkv"
      },
      "export-result": {
        "operation": "export/url",
        "input": "convert"
      }
    }
  }'

# 2. Upload your file (use upload_url from the response)
curl -X PUT "$UPLOAD_URL" --upload-file input.asf

# 3. Poll for result
curl https://api.runconvert.com/v3/jobs/$JOB_ID?include=tasks \
  -H "Authorization: Bearer YOUR_API_KEY"

Replace YOUR_API_KEY with your RunConvert API key. Get your free API key at runconvert.com/api.