Free online HEVC to FLV converter

Some older streaming, broadcasting, and video-editing applications accept FLV but cannot open HEVC video. Converting the file usually requires decoding H.265 and re-encoding it as H.264 inside an FLV container, because legacy FLV players have limited HEVC support.

What the HEVC format is

HEVC, also called H.265, is a video compression standard designed to deliver similar visual quality to H.264 at lower bitrates. Phones, action cameras, screen-recording applications, OBS Studio, and modern video editors commonly create HEVC files, usually with .mp4, .mov, or .mkv containers. HEVC is common in 4K recordings and newer smartphone videos, but older software may lack the decoder required to open it.

What the FLV format is

FLV is a Flash Video container developed for web streaming. It was widely used by older Flash-based video sites and applications because it supported progressive download, metadata, and synchronized audio and video in a compact container.

For broad legacy compatibility, FLV normally contains H.264 video and AAC or MP3 audio. Flash itself is obsolete and no longer supported by current web browsers, so FLV is mainly useful when a specific legacy encoder, player, broadcast workflow, or application requires it.

How to convert HEVC to FLV

Using FFmpeg

FFmpeg provides the most controllable desktop conversion method. Install a current FFmpeg build, open a terminal in the folder containing the source, and run:

ffmpeg -i input.mp4 -c:v libx264 -pix_fmt yuv420p -c:a aac -b:a 128k -ar 48000 -f flv output.flv

Replace input.mp4 with the actual HEVC filename and output.flv with the desired output name. The command decodes HEVC, encodes video as H.264, converts audio to AAC, and writes an FLV container.

To control video size and bitrate, add settings such as:

ffmpeg -i input.mp4 -vf scale=-2:720 -c:v libx264 -preset medium -crf 23 -pix_fmt yuv420p -c:a aac -b:a 128k -f flv output.flv

scale=-2:720 limits the height to 720 pixels while preserving an even width. Lower -crf values increase quality and file size; values around 18–23 are common for H.264 output. Use -preset fast for shorter encoding time or -preset slow for better compression at the same quality setting.

Using a graphical application

In a desktop video converter that supports FFmpeg-based encoding, import the HEVC file, choose Export or Convert → Video → FLV, select H.264 as the video codec, AAC as the audio codec, and start the conversion. If the application exposes container and codec separately, choosing FLV alone is not sufficient; set H.264 and AAC explicitly for older players.

Converting without installed software

You can convert the file for free on the 101convert.com website without installing software. Select the HEVC file, choose FLV as the output format, start the conversion, and download the resulting file when processing finishes.

Quality, compatibility, and limitations

Because HEVC must normally be re-encoded as H.264, the conversion is not lossless and takes longer than a simple container remux. Use a lower CRF value or a higher target bitrate when preserving detail matters; converting a previously compressed recording cannot restore lost quality.

FLV supports only a limited set of codecs reliably across older software. H.264 video with AAC audio is the safest combination, while HEVC, high-bit-depth video, HDR metadata, subtitles, chapters, and multiple audio tracks may be discarded or ignored. Check the output with the target application rather than relying only on the .flv extension.

For a file with no audio stream, use -an instead of the audio options. For a source with several audio or subtitle tracks, specify the required streams explicitly, for example -map 0:v:0 -map 0:a:0; unsupported subtitle streams should generally be omitted from FLV.