Why won't my iPhone play MKV files?

iOS doesn't natively support the MKV container. iPhone can play H.264 and HEVC video content, but only inside MP4 or MOV containers. Converting the MKV to MP4 solves this without any quality loss if the video codec is compatible.

Will I lose video quality converting MKV to MP4?

Not if the MKV uses H.264 or HEVC video and AAC audio — which is typical for downloaded content. FFmpeg re-wraps the streams into an MP4 container without re-encoding. Quality is bit-for-bit identical.

Can I play the converted MP4 on my Smart TV?

Yes — MP4 with H.264 video is the most widely supported video format. Every Smart TV from the last decade supports it natively.

Why does Plex transcode my MKV files?

Plex transcodes MKV files that use codecs its client device doesn't support directly. Converting to MP4 with H.264/AAC tells Plex the file is already in a direct-play compatible format, eliminating transcoding.

What's the maximum file size?

100MB per file. Feature-length MKV movies are typically 1–15GB, which exceeds this limit — for large files, use HandBrake or desktop FFmpeg.

Are my video files uploaded to your server?

No. FFmpeg.wasm processes everything in your browser.

What if my MKV has multiple audio or subtitle tracks?

The converter selects the primary audio track. Subtitle tracks are not included in the MP4 output.

Does this work for short MKV clips under 100MB?

Yes — short clips, screen recordings, and edited MKV exports under 100MB convert quickly and cleanly.

MKV to MP4 Converter

Convert MKV to MP4 free online — no upload, no signup. Fix MKV playback on iPhone, Smart TV & Plex. Browser-based, 100% private. No re-encoding when possible.

FileConvertir — Free Online File Converter