MP4 to FLV Converter
Flash Player is gone, but its container lives on inside RTMP streaming and a few legacy systems that still ask for .flv. This page wraps an MP4 into Flash Video for exactly those cases.
Video Converter
or drop MP4, MOV, MKV … files here ·
Max 95 MB per file· Up to 20 files· Deleted after 30 minutes
Files are processed on our servers and deleted after 30 minutes.
Lower is better quality and a bigger file. 18 looks identical to the source, 23 is the default, 28 and above shows visible softening.
Frames per second. Keep the source rate unless a platform asks for a specific one; 15–20 fps is plenty for GIFs.
Only used for PowerPoint files and single still images: how long each slide or picture stays on screen.
Auto uses AAC for MP4/MOV and Opus for WebM. Copy keeps the original sound untouched when the new format supports it.
192 kbps is transparent for music; 128 kbps is enough for speech.
Width of the animation in pixels; height follows the aspect ratio. 480 px suits chats, 720 px or more gives a high-quality GIF but a much larger file.
GIF holds at most 256 colors. Fewer colors make a smaller file but cause banding on gradients and skin tones.
Mixes palette colors in a fine pattern to hide banding. Sierra gives the smoothest result; none gives the smallest file.
Whether the animation repeats endlessly or plays one time and stops.
Optional. Seconds (e.g. 75) or minutes:seconds (1:15). Leave empty to start at the beginning.
Optional. Same format as the start time. Leave empty to keep everything up to the end.
The converted file will be at or just under this size.
How to use this tool
- 1
Upload the MP4
Add one MP4 or a batch of up to 20, each up to 95 MB. MOV, MKV and WebM sources are accepted too.
- 2
Check the audio setting
Audio codec starts on AAC, the codec RTMP servers and flv.js expect. Lower Resolution to 720p if the FLV is for a slow ingest link.
- 3
Press Convert to FLV
Download the .flv files one by one or as a ZIP. Everything is removed from the server after 30 minutes.
Upload an MP4 and press Convert to FLV. You get Flash Video with AAC sound, the pairing that RTMP servers, flv.js and Flash Player 9 Update 3 or later all read.
Why convert MP4 to FLV after the end of Flash
Macromedia built FLV for Flash Player 6 in 2002, starting with the Sorenson Spark codec, and added On2 VP6 in Flash Player 8. The format turned modern in December 2007, when Flash Player 9 Update 3 learned H.264 video and AAC audio; from then on an FLV could hold the same streams as an MP4.
Adobe ended Flash Player on December 31, 2020, yet the container never left streaming. Every RTMP push from an encoder is a sequence of FLV tags, and some test rigs, restreaming scripts and media servers such as nginx-rtmp or SRS are easiest to feed with a file that is already FLV. A smaller group of users has a training portal or kiosk built in the Flash years that lists .flv as its only upload type.
| from ↓ · to → | H.264 | HEVC | AV1 | AAC | MP3 |
|---|---|---|---|---|---|
| Classic FLV | Classic FLV to H.264: yes | – Classic FLV to HEVC: no | – Classic FLV to AV1: no | Classic FLV to AAC: yes | Classic FLV to MP3: yes |
| Enhanced RTMP FLV | Enhanced RTMP FLV to H.264: yes | Enhanced RTMP FLV to HEVC: yes | Enhanced RTMP FLV to AV1: yes | Enhanced RTMP FLV to AAC: yes | Enhanced RTMP FLV to MP3: yes |
| MP4 | MP4 to H.264: yes | MP4 to HEVC: yes | MP4 to AV1: yes | MP4 to AAC: yes | MP4 to MP3: yes |
MP4
MPEG-4 video
MP4 (MPEG-4 Part 14) is a multimedia container standardised by ISO/MPEG and based on Apple's QuickTime format. It usually holds H.264 or HEVC video with AAC audio, and can also carry subtitles, chapters and metadata. It is the most compatible video format in the world, playing on phones, browsers, TVs, game consoles and social platforms. The video inside is almost always lossy, so repeated re-encoding gradually reduces quality.
- Compression
- Lossy
- Transparency
- –
- Animation
- –
- Introduced
- 2001 · Moving Picture Experts Group (MPEG)
FLV
Flash Video
FLV is the Flash Video container that Macromedia, later Adobe, introduced in the early 2000s for streaming video in Flash Player. It powered early YouTube and many video sites, and the FLV format is still used by some RTMP live-streaming tools. With Flash Player discontinued in 2020, browsers and phones no longer play FLV files. VLC and other desktop players still open them.
- Compression
- Lossy
- Transparency
- –
- Animation
- –
- Introduced
- Macromedia (now Adobe)
MP4 goes to FLV for the machinery rather than the viewer: an RTMP ingest test, a flv.js player or a Flash-era LMS that only lists .flv as an accepted upload.
Where an FLV made from an MP4 ends up
Testing an RTMP server
Streaming engineers loop a short FLV into a local server to check ingest, transcoding and recording before a real event. Since the file already uses FLV packaging, the push needs no remux step.
A flv.js or legacy web player
Pages built around flv.js or an old Flash-fallback player expect a progressive .flv. Keep the video at H.264 and the audio at AAC so the browser can decode what the library unwraps.
An old LMS or kiosk
Training packages from the late 2000s often hard-code .flv paths. Replacing a clip with a new FLV of the same name is usually the fastest fix, and 720p is a safe ceiling for those players.
What changes when MP4 becomes FLV
FLV is a much thinner container than MP4. It carries one video and one audio stream, with no chapters, no subtitle tracks, no second language and no rotation flag, so a portrait phone clip that relies on the MP4's rotation metadata can play sideways. Rotate or crop it before you convert if that matters.
Size barely moves when the codec stays the same, so an MP4 under the 95 MB upload limit gives an FLV of a similar size. If the destination has its own cap, the video compression guide shows how resolution and bitrate trade against each other, and the video converter page explains every option on this tool.
MP4 to FLV converter FAQ
Who still uses FLV files in 2026?
Mostly streaming infrastructure. RTMP, the protocol OBS and most encoders use to push a live feed to YouTube or Twitch, carries its audio and video in FLV tags, and tools such as FFmpeg write the stream with the flv muxer. Outside streaming, it survives in old e-learning packages, kiosk players and archived sites.
Can a browser play an FLV without Flash?
Not on its own; no current browser has an FLV decoder. Sites that still deliver FLV use flv.js, an open-source library Bilibili released in 2016 that unpacks the FLV in JavaScript and hands the H.264 and AAC inside to the browser's own media engine.
Will the FLV be larger than the MP4?
Close to the same size when the picture stays H.264, because the container adds only a few bytes per frame. The size jumps only if a player forces you onto older codecs such as Sorenson Spark, which need far more bits for the same detail.
Can I put HEVC or AV1 video in an FLV?
Only in the Enhanced RTMP extension published in 2023, which OBS Studio 29.1 used to stream HEVC and AV1 to YouTube. A classic FLV parser rejects those streams, so for any legacy player keep the video at H.264.
Why does my FLV seek slowly in VLC?
An FLV has no central index unless the writer adds keyframe metadata to the header, so a player may have to scan the file to find a jump point. Short clips are unaffected; for long recordings, convert back with FLV to MP4 once the FLV has served its purpose.
Does the FLV keep chapters or subtitles from my MP4?
No. FLV has no chapter list and no subtitle track type, so both are dropped. If captions matter, burn them into the picture in an editor before converting, or keep the MP4 alongside the FLV.
