FLV to HEVC Converter

FLV to HEVC — or FLV to MP4 With H.265?

Almost everyone who searches for "FLV to HEVC" wants one thing: an old Flash Video clip re-encoded with H.265 so it takes less space. There are two ways to get that, and they differ only in the wrapper. This page writes a .hevc file, which in our pipeline is muxed with the Matroska muxer and carries the FLV's audio track alongside the H.265 video. That plays in VLC 3.0+ and mpv but not in QuickTime, phone galleries or browsers. If you want the same H.265 video in a file that opens everywhere, use FLV to MP4 and set the video codec to H.265. Short answer: pick .hevc if your tools speak Matroska, pick MP4 if people have to watch it.

Side-by-side Comparison

When to Pick .hevc

• Your player or toolchain is VLC, mpv, ffmpeg or anything else that reads Matroska regardless of the file extension.
• You specifically need a file named .hevc to satisfy a downstream script or an ingest folder.
• You want Matroska's freedom to carry extra audio or subtitle tracks later.
• You are archiving and will rename to .mkv yourself when it is time to play the file.

When to Pick MP4 or MKV Instead

• Anyone else has to watch it. MP4 is the only one of the three that opens in a browser, on a phone gallery, or in QuickTime.
• You are uploading to a platform or messaging app that validates the extension before it looks at the bytes.
• You want a plain .mkv that media servers and TV apps recognise without you renaming the file first.
• You are not sure — in which case MP4 is the safe default and costs nothing in compression, because it carries the identical H.265 video.

Codecs: What Your FLV Probably Holds, and What Replaces It

How to Convert FLV to HEVC

1. Upload Your FLV File: Drag and drop the .flv onto the page or click "+ Add Files". Several clips can be queued and converted with the same settings.
2. Check Video Codec and Audio Codec: Under "Video Codec" the list shows both "H.265" and "HEVC" — they resolve to the same encoder, and H.265 is preselected. "Audio Codec" is preselected to AAC, with AC3, DTS (DCA), EAC3, FLAC, MP2, MP3, Opus and Vorbis available.
3. Set the compression mode, resolution or trim: "File Compression" starts on "Quality Preset" at "Very High (Recommended)"; "Specific file size", "Constant Bitrate", "Variable Bitrate", "Constant Quality" and "Constraint Quality" are the alternatives. "Video resolution" starts on "Keep original", and "Trim" can be switched from "Unchanged" to "Time Range" with a start time and duration.
4. Convert and Download: Click "Convert" and save the .hevc file. It uploads over an encrypted connection, is processed on our servers and is deleted automatically after a few hours — no sign-up, no watermark.

Frequently Asked Questions

Why will my .hevc file not play in QuickTime or on my phone?

Because the bytes are Matroska, and QuickTime, the Windows Photos app, phone galleries and browsers do not read Matroska — on top of which H.265 decoding itself is missing on older hardware. VLC 3.0+ and mpv open the file directly, audio included, with a working seek bar. Renaming it to .mkv satisfies software that judges by extension. If you need something universally playable, convert with FLV to MP4 instead.

Does the .hevc file keep my FLV's audio?

Yes. FLV clips normally carry MP3, AAC, ADPCM, Nellymoser or Speex audio, and that track is re-encoded — to AAC unless you choose otherwise — and stored alongside the H.265 video in a normal track structure. If an app plays the file silently or rejects it, that is a Matroska or codec gap in the app, not a missing audio track.

Should I choose "H.265" or "HEVC" in the Video Codec list?

It makes no difference to the output. H.265 and HEVC are two names for the same ITU-T/ISO-IEC standard, and both entries route to the same encoder in our pipeline. H.265 is the preselected entry; leaving it alone is correct.

Will converting to H.265 make my old FLV look better?

No. H.265 compresses more efficiently than the codecs an FLV carries, but efficiency is not restoration. Whatever Sorenson Spark or VP6 discarded at 320x240 in 2006 is gone, and re-encoding carries the remaining quality forward at best. Expect a smaller file at similar visual quality, not a sharper picture.

Is FLV to HEVC lossless?

No, and it cannot be. An FLV never contains an H.265 stream, so every frame has to be decoded and re-encoded — a full transcode that adds a generation of lossy compression on top of the Flash-era one. Keep the original FLV as the master. To minimise the added loss, leave "Quality Preset" high and avoid downscaling the resolution unless you need to.

Will the output actually be smaller than the FLV?

Usually, but not always. Old FLVs are often already at very low bitrates, and re-encoding a 400 kbps VP6 clip with a high-quality H.265 preset can produce a larger file, because the encoder is being asked for more fidelity than the source has. If size is the goal, use "Specific file size" or "Constant Bitrate" under File Compression and name the target rather than relying on the quality preset.

Which audio codec should I pick?

AAC, unless you have a reason not to — it is preselected, widely supported and efficient. AC3 or EAC3 make sense if the file is destined for a home-cinema chain that expects them; Opus is the most efficient at low bitrates; FLAC is lossless but will not recover quality, because the FLV's audio was already lossy, so it only inflates the file size.

Can I convert just one section of the clip?

Yes. Set "Trim" to "Time Range" and give a start time and a duration, in seconds or as HH:MM:SS.sss. That is done during the same encode, so you do not need a separate cutting step.

What happens to my file after conversion?

It is uploaded over an encrypted connection, decoded and re-encoded on our servers, and deleted automatically after a few hours along with the output. No sign-up, no watermark, never shared or made public. The practical limit on very large sources is upload size and time.