Step 1: Supply your FLV files using the button above or by haul and lay.
Step 2: Click the 'Convert' button to start the conversion.
Step 3: Get your converted MKV files.
FLV to MKV Conversion FAQ
What does the FLV to MKV converter do?
+
FLV is a legacy container, often poorly supported on modern devices. Converting to MKV rewraps the video with a current codec (H.264 / H.265 / VP9) for broad browser, phone, and TV compatibility.
Will resolution and frame rate be preserved in the MKV?
+
Yes. FLV → MKV keeps resolution, frame rate, and aspect ratio unchanged by default. To change them, use the Resize or Speed tool on the result.
Will the FLV play smoothly on modern devices after converting to MKV?
+
Yes. Legacy FLV files often fail to play in modern browsers and on iOS / Android. MKV uses widely supported codecs that play natively on phones, tablets, smart TVs, and every modern browser.
Will the converted MKV be a different size than the FLV?
+
Modern codecs compress better, so MKV from a legacy FLV is typically 30-60% smaller at equivalent quality. Conversions in the opposite direction can grow the file.
Can I add selectable subtitles once the file is MKV?
+
Yes. FLV has no usable soft-subtitle track, so subtitles for FLV content had to be burned into the picture or shipped as a separate sidecar file. MKV carries subtitles as their own selectable stream, so after conversion you can attach an SRT track the viewer can switch on, switch off or restyle. MKV is codec-agnostic: H.264, HEVC, VP9 and AV1 video sit happily beside AAC, FLAC, Opus, DTS or Dolby audio in the same file.
Why do so many people keep their libraries in MKV?
+
Because it was designed for keeping things rather than for delivering them. An MKV holds an unlimited number of audio tracks, selectable subtitle streams, chapter marks and cover art in one file, which is exactly what a disc rip needs somewhere to put — everything ends up in a single object instead of a folder of loose companions. The trade is playback: very little consumer hardware decodes it natively, so the same file that is ideal on a computer or a media server usually has to be converted again before a television will touch it. MKV is the archival container of choice because it stores unlimited audio tracks, soft subtitles, chapter markers and cover art in one file.
Can the MKV hold more than one audio track?
+
Yes, and it is a real upgrade over FLV. MKV treats every audio stream as a first-class track, so an original-language mix, a dub and a director commentary can live in one file with the player switching between them on demand.
Does MKV support chapter markers that FLV did not?
+
It does. MKV stores chapters as container metadata, so a long recording can be navigated by section instead of by scrubbing a progress bar. FLV has nowhere to put that information, so if the source shipped with a chapter list it was in a sidecar file — hand that to the converter and it gets written into the MKV.
Is it worth converting old FLV recordings to MKV at all?
+
For anything you intend to keep, yes. FLV belongs to an earlier generation of video tooling and the software that reads it is steadily disappearing from phones, browsers and operating systems. Moving the footage to MKV now, while a clean decoder still exists, is the difference between an archive you can open in ten years and one you cannot. No current browser, phone or TV can play FLV — anything still in this container has to be moved out of it to remain watchable.
Is there a file-size limit when converting FLV to MKV?
+
Anonymous uploads are capped at a generous default; signed-in free accounts get a higher cap, and Pro accounts have no per-file limit. Browser memory is usually the practical constraint long before our server-side limits kick in.
Can I batch-convert several FLV files to MKV at once?
+
Yes. Drop or pick multiple FLV files in one upload — the converter processes them in parallel and returns a ZIP of the MKV results. There is no need to repeat the upload step per file.
What happens to my FLV files after the conversion?
+
Uploaded files and MKV outputs are auto-deleted after a short retention window. We do not inspect, share, or train on user files. Direct download links are time-limited and tied to your session.
