The Flash Video format packages Sorenson Spark or VP6 video in Adobe's Flash container, now largely obsolete following the end of Flash Player support. Converting to MKV produces a video file that stores video, audio, subtitles, and chapters in an open-standard container that supports virtually every codec. This conversion changes the file's encoding, compression method, and supported feature set. Metadata such as creation date and embedded colour profiles is preserved where the target format supports it. This makes MKV the practical choice when the destination system requires it or when the target format offers better compatibility or compression. 1converter runs this conversion on the server: your file is uploaded encrypted over HTTPS, converted using trusted open-source libraries, and the output is held for 24 hours before automatic deletion.