Source format
FLV is a legacy web video container with limited support in modern browsers and devices.
FLV
FLV (Flash Video) is a video container that was used by Adobe Flash Player for web video. It typically holds H.264, VP6, or Sorenson Spark video with AAC or MP3 audio. Browsers no longer support Flash, so FLV files are usually converted to MP4.
MKV
MKV (Matroska Video) is a flexible open-source video container. One MKV file can hold multiple video, audio, and subtitle tracks plus chapters, which makes it popular for movies and series. Many TVs and phones play MKV, but MP4 is supported more widely.
What happens when FLV becomes MKV
Target format
MKV is a flexible Matroska container that can carry multiple audio, video, and subtitle tracks.
What changes
The FLV container is read and the selected video and audio streams are written into a MKV container.
Codecs may be transcoded even when the visible resolution and duration stay the same.
- What is preserved
- Duration, frame order, and visible dimensions are preserved unless you select trimming, frame-rate, or resolution changes.
- What may be lost
- Extra subtitle, attachment, chapter, or alternate audio tracks may be omitted when the target container or selected settings do not support them.
- Codec and quality implications
- Container names do not guarantee a codec. Quality and compatibility depend on the selected video codec, audio codec, bitrate, frame rate, and resolution.
- Realistic limitations
- A valid FLV extension does not guarantee that every codec inside the container is decodable. Corrupt, encrypted, or unusual streams can fail.
Conversion steps
- Upload a FLV file no larger than 1 GB.
- Confirm that MKV is selected as the target.
- Open settings only if you need to change codec, quality, bitrate, frame rate, resolution, or audio behavior.
- Start the conversion. A healthy compatible worker begins processing immediately.
- Download the MKV file and check the result before deleting your source.
Troubleshooting
- The FLV file is rejected or will not open.
- Confirm that the file is not empty, password-protected, or corrupt and that its real format matches the extension.
- The MKV file is larger than expected.
- Choose a more efficient codec or lower quality setting when available. Lossless and uncompressed targets are often larger by design.
- The result has no sound or will not play.
- Try a broadly supported target codec and verify that the source contains a decodable audio stream.
Privacy and file retention
Uploads and converted files are processed automatically and irreversibly deleted within 24 hours. You can delete them sooner with the delete control. Convertr does not read, mine, sell, or manually review file contents.
Read the privacy policy