Free online H265 to FLV converter

What the H.265 format is

H.265, also called HEVC, is a video codec rather than a container. It compresses video more efficiently than H.264, so cameras and phones can store 4K or high-frame-rate footage at lower bitrates. HEVC video commonly appears inside MP4 or MKV files, or as a raw elementary stream with an .h265 or .hevc filename.

Recent smartphones, mirrorless cameras, action cameras, OBS Studio configurations, and editing applications can create HEVC video. Older players, browsers, and Flash-era publishing tools may not decode it.

What the FLV format is

FLV is a container designed for Flash Video streaming. It can hold video encoded with codecs such as H.264, VP6, or Sorenson Spark, and audio encoded with AAC or MP3. It was widely used by older web video platforms and Flash-based players.

FLV remains useful when a legacy application, embedded player, broadcast tool, or archive workflow specifically requires an FLV container. Its main advantage for this conversion is compatibility with older systems, not better quality or smaller files. Most current browsers and players favor MP4, WebM, or fragmented streaming formats instead.

How to convert H.265 to FLV

For desktop conversion, FFmpeg is suitable because it can decode HEVC and encode the broadly supported H.264/AAC combination used in FLV files. Install FFmpeg, open a terminal in the folder containing the source, and run:

ffmpeg -i input.mp4 -c:v libx264 -pix_fmt yuv420p -preset medium -crf 23 -c:a aac -b:a 128k output.flv

Replace input.mp4 with the actual HEVC source, including input.mkv or input.h265. For a raw HEVC elementary stream, specify the input format if FFmpeg does not detect it:

ffmpeg -f hevc -i input.h265 -c:v libx264 -pix_fmt yuv420p -preset medium -crf 23 -an output.flv

The second command uses -an because a raw H.265 stream normally contains video only. If the source has audio, use -c:a aac -b:a 128k instead of -an.

For a larger file with higher visual quality, lower the CRF value; for a smaller file, raise it. A range of 18–28 is commonly practical, with 23 as a starting point. The libx264 encoder is required because H.265 is not reliably supported by FLV players. If your FFmpeg build lacks that encoder, install a build with x264 support or use a desktop transcoder that offers H.264 output and FLV as the container.

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

Quality and compatibility limitations

This process re-encodes HEVC as H.264, so it is not lossless and cannot preserve the original compression efficiency. Do not use -c:v copy: that only remuxes the stream and commonly produces an FLV file that older FLV software cannot decode because it still contains HEVC.

Use -pix_fmt yuv420p for compatibility with older decoders. HEVC sources with 10-bit color, HDR, unusual frame rates, or multichannel audio may require additional conversion; standard H.264 FLV workflows generally target 8-bit SDR video and AAC audio. Verify the result with a player or the target application, because an FLV extension alone does not guarantee that its embedded codecs are supported.