Step 1: Transfer your FLV files using the button above or by slide and deposit.
Step 2: Click the 'Convert' button to start the conversion.
Step 3: Retrieve your converted MKV files.
FLV to MKV Conversion FAQ
How do I re-encode FLV to MKV without losing video quality?
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Upload your FLV file and the converter runs a CRF-based re-encode targeting visually-lossless MKV output (CRF 18 by default, lower values = larger file / higher quality). The codec is chosen to match the MKV container — H.264 for broad-compat MP4, H.265 for size-efficient MKV, VP9 for WebM, AV1 for newer pipelines. FLV typically holds Sorenson Spark or H.264 video with MP3 or AAC audio, wrapped in a stream format designed for RTMP delivery. 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.
Can I add selectable subtitles once the file is MKV?
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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.
Can the MKV hold more than one audio track?
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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. MKV is the archival container of choice because it stores unlimited audio tracks, soft subtitles, chapter markers and cover art in one file.
Does MKV support chapter markers that FLV did not?
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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?
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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.
Which video codec does the MKV output use?
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It depends on the MKV container. MP4 defaults to H.264 for the broadest playback support across phones, browsers, and Smart TVs. MKV defaults to H.265 / HEVC for roughly half the file size at equivalent quality. WebM defaults to VP9. The advanced options expose explicit codec choice if you need to override. MKV is Matroska, an open container designed in 2002 with no licensing restrictions and no ceiling on what it can hold.
Will my audio track survive FLV to MKV conversion?
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Yes. When FLV and MKV share an audio codec (e.g. both carry AAC), audio is re-muxed with no re-encode — bit-identical. When the codecs differ, audio is transcoded to AAC / Opus / Vorbis depending on what the MKV container supports. Multi-track audio (commentary, alternate languages) is preserved.
Can I keep the original framerate when converting FLV to MKV?
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By default yes — a 24fps FLV stays 24fps in MKV; a 60fps FLV stays 60fps. If you need to change rate (e.g. interlaced 29.97 → progressive 30, or 60 → 30 for upload limits), the framerate option handles 3:2 pulldown, deinterlacing, and frame-blending in the same encode pass.
How much will the file size change going from FLV to MKV?
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Same-codec re-mux (FLV H.264 → MKV H.264 just changing container): nearly identical size. Codec change can swing dramatically: H.264 → H.265 typically halves the file at the same visual quality; VP9 is roughly comparable; AV1 cuts another 20-30% but is slower to encode.
Will the MKV file play on iPhone, Android, and Smart TVs?
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MP4 / H.264 plays natively on every modern device. MOV / H.264 plays on Apple devices and most TVs but not always on older Android. MKV needs VLC on iOS. WebM is browser-first. The advanced options include a "device compatibility" preset that picks the safest MKV codec / container for your target. MKV has almost no native hardware support — phones, browsers and TVs usually need VLC or a remux before they will play it.
How long does converting a 1-hour FLV video to MKV take?
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Same-codec re-mux is near-instant — 30 to 60 seconds for a 1-hour file. A full codec re-encode runs at roughly 0.3-0.7x source duration on our GPU pipeline, so a 1-hour FLV → MKV finishes in 18-40 minutes depending on resolution and target codec.
What is the maximum resolution supported for FLV to MKV?
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Up to 8K (7680×4320) on Premium plans. Free conversions are capped at 4K (3840×2160) by the per-file size limit. HDR metadata (HDR10, HDR10+, Dolby Vision when present) is carried through where both FLV and MKV containers support it.
FLV (Flash Video) is a video container format developed by Adobe. It is commonly used for online video streaming and is supported by Adobe Flash Player.
