Free · No Upload · Instant

Convert WEBM to MKV Free Online — Best WEBM to MKV Converter 2025

Convert WEBM to MKV online for free. Fast, private WebM Video to Matroska Video converter — no upload, no signup. Works in your browser instantly.

Choose Files

or drag and drop files here

Max file size: 2GB

Your files are processed locally in your browser. Nothing is uploaded to any server.

How to Convert WEBM to MKV

Upload your WEBM file by clicking "Choose Files" or drag and drop it.

Select MKV as the output format.

Click "Convert Now" and download your converted file.

About WEBM Format

Extension: .webm
Full name: WebM Video

About MKV Format

Extension: .mkv
Full name: Matroska Video

Frequently Asked Questions

Is it safe to convert WEBM to MKV online?

Yes! Convert999 processes all files directly in your browser. Your files are never uploaded to any server, ensuring complete privacy and security.

How long does it take to convert WEBM to MKV?

Conversion is nearly instant for most files. Large files may take a few seconds depending on your device's processing power.

Is there a file size limit?

Convert999 supports files up to 2GB. Processing happens locally, so larger files depend on your device's available memory.

Do I need to install any software?

No installation required. Convert999 works entirely in your web browser on any device.

Can I convert WEBM to MKV on my phone?

Yes! Convert999 works on any device with a web browser — iPhone, Android, iPad, or desktop. No app installation required. Simply open the converter, upload your WEBM file, and download the converted MKV file.

Will I lose quality converting WEBM to MKV?

Convert999 uses high-quality conversion algorithms to minimize quality loss. For lossless formats, the conversion is exact. For lossy formats like images and audio, we use optimized settings that balance quality and file size.

Can I batch convert multiple WEBM files to MKV?

Yes, Convert999 supports batch conversion. Select or drag & drop multiple WEBM files and convert them all to MKV format at once. Each file is processed locally in your browser.

What is the difference between WEBM and MKV?

WebM Video (WEBM) and Matroska Video (MKV) differ in compression, compatibility, and features. WEBM is optimized for its native use cases, while MKV may offer different advantages. Visit our WEBM vs MKV comparison page for a detailed breakdown.

Why Convert WEBM to MKV?

Advantages

✓Matroska Video offers better compatibility with modern applications and workflows
✓Converting is completely free with no file size limits on Convert999
✓Your files never leave your device — 100% private and secure conversion
✓Instant conversion without waiting for server processing

Key Differences

→WEBM (WebM Video) is optimized for its native use cases
→MKV (Matroska Video) may offer different compression or feature set
→Choose based on your target platform, quality needs, and file size requirements

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