MKV to FLV Converter

How to Convert MKV to FLV Online

1. Upload Your MKV File: Drag and drop or click "Add Files" to select MKV files. Movie rips, anime releases, lecture recordings, and Blu-ray remuxes all work. Batch is supported — drop in multiple MKV files for sequential conversion.
2. Pick a Video Codec for the FLV: Default is FLV (Sorenson H.263) — the original codec the format shipped with and the one every legacy Flash player decodes. Switch to H.264 if your target player or CMS supports the post-2008 FLV-with-AVC profile (most modern Flash 9+ players do). Set a quality preset (Highest → Lowest), target a percentage of the source size or an exact size in MB, dial in a constant or variable bitrate, or fine-tune with QSCALE quality (lower = better).
3. Resize or Trim (Optional): Pick a resolution preset (480p / 360p / 240p match typical Flash-era video; 720p / 1080p require H.264-in-FLV), enter custom width × height, scale by percentage, or trim using start time + duration in seconds or HH:MM:SS.sss. FLV's Sorenson codec was designed for sub-720p web video — downscale large modern MKV sources to keep playback smooth on legacy decoders.
4. Convert and Download: Click Convert. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — no sign-up, no watermark, never shared.

Why Convert MKV to FLV?

MKV (Matroska) is the modern open container behind most current HD/4K video — H.264, H.265, and AV1 streams wrapped with multi-track audio, subtitles, and chapters. FLV (Flash Video) was the dominant web video format from 2002 to about 2015, the format YouTube, Vimeo, and most streaming sites used during the Flash era. Adobe officially ended Flash Player on December 31, 2020, and modern browsers no longer load it — so the use cases for converting into FLV in 2026 are narrow and specific. They exist:

• Feeding legacy CMS and LMS platforms — Older Moodle, Blackboard, and SharePoint deployments, plus internal corporate training portals built in 2008-2014, still expect .flv uploads in their video module. Re-encoding an MKV master to FLV is the only way to get the file accepted by the upload form.
• Archival parity with an existing FLV library — When you already have hundreds of FLV recordings (old webinars, Camtasia screen captures, Articulate Storyline output), converting new MKV captures to FLV keeps the archive in one consistent format for cataloguing and bulk indexing.
• Restoring playback on offline Flash projector kiosks — Museums, trade-show booths, and information kiosks built around the standalone Flash Projector (flashplayer_sa.exe) still run offline. They never required a browser and aren't affected by the 2020 EOL — they need FLV input.
• Industrial / embedded systems with FLV-only firmware — Some pre-2015 IP cameras, digital signage controllers, and DVR appliances output and re-ingest FLV exclusively. New footage captured as MKV needs converting before the appliance will accept it.
• Legacy Adobe Animate (Flash) project assets — Reauthoring an old Flash CS6 / Animate project that imports .flv via NetStream or the FLVPlayback component requires the source asset in FLV form. MKV won't import.
• VLC / MPC-HC archive playback consistency — Modern players like VLC and MPC-HC still play FLV cleanly. Keeping legacy training material in FLV preserves the original viewing experience exactly as users remember it.

For modern web use cases (browser embedding, social sharing, mobile playback) convert to MKV to MP4 or MKV to WebM instead — those are the formats that actually play in 2026.

MKV vs FLV — Format Comparison

Codec Choice for the FLV Output

Frequently Asked Questions

Why would I convert anything to FLV in 2026?

Niche compatibility — that's the only reason. Adobe ended Flash Player on December 31, 2020, and no modern browser loads it. Conversions to FLV exist for legacy CMS/LMS uploads that still validate by extension, offline Flash Projector kiosks, pre-2015 industrial appliances with FLV-only firmware, and parity with existing FLV archives. For anything that needs to play in a 2026 browser, convert MKV to MP4 or WebM instead.

Will VLC and MPC-HC still play the converted FLV?

Yes. Both VLC and MPC-HC ship with native FLV demuxers and decode Sorenson H.263, VP6, and H.264-in-FLV without Flash Player. The 2020 Flash EOL only affected browser plugins and the standalone projector's network features — desktop video players were never dependent on the Flash runtime.

Should I pick the FLV codec or H.264 inside FLV?

Pick the FLV (Sorenson H.263) codec when targeting genuinely old Flash players or CMS upload validators that pre-date Flash Player 9 (2007). Pick H.264 when the target system is newer — Flash Player 9.0.115+, modern projector apps, post-2008 LMS — because H.264 is roughly 3-4× more efficient and lets you keep HD resolutions at sane file sizes. If you don't know which the target accepts, FLV/Sorenson is the safer default.

Will multi-audio tracks and subtitles from the MKV survive?

No. FLV supports a single audio track and has no native subtitle stream. The conversion keeps the primary audio (usually English or whatever's flagged as default in the MKV) and drops alternates. Subtitles must be burned into the picture before conversion or saved separately as an external file the player loads alongside the FLV.

Will the FLV be larger or smaller than the source MKV?

Usually larger per minute when using the original FLV (Sorenson) codec, because Sorenson H.263 is roughly 4-5× less efficient than H.265 and 2-3× less efficient than H.264. A 1.5 GB H.265 MKV often becomes a 3-4 GB FLV at similar visual quality. Picking H.264-in-FLV closes most of that gap. Downscaling to 480p or 360p (the resolution Flash-era video actually targeted) is the practical way to keep file size in check.

Can I convert a 1080p or 4K MKV directly to FLV?

Technically yes with H.264-in-FLV, but the original FLV/Sorenson codec was designed for sub-720p web video and most legacy Flash players cap at 720p or lower. If your target is a real Flash 8 projector or an old LMS, downscale to 480p or 360p first. If your target is a modern Flash Projector or a player that accepts H.264-in-FLV, full HD is fine — but at that point MP4 is almost always the better container.

Can I trim the file while converting?

Yes. Use the trim section to enter a start time and duration. Both accept seconds (12.5) or HH:MM:SS.sss format (00:01:30.500). Useful for snipping out intros, recap reels, or post-credits before pushing the file into an LMS that has tight per-file size limits.

Can I batch convert an entire MKV folder to FLV?

Yes — drop in multiple MKV files and they convert sequentially on our servers. Each download is a separate .flv file. Set the codec, bitrate, and resolution once and run the whole folder. Useful for migrating a library of new MKV captures into an existing FLV archive in one pass.

Does the converted FLV embed in old Flash CS6 / Animate projects?

Yes — the output is a standard .flv file that the FLVPlayback component and NetStream API both accept. For the Sorenson-codec output, every Flash version from 6 onward plays it. For the H.264-in-FLV output, you need Flash Player 9.0.115+ (2007) at runtime. Re-publishing the project SWF picks up the new file automatically.