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MP4 to FLV converter

Convert MP4 to FLV in your browser. No upload and no account: the file never leaves your device, so the only size limit is your device’s memory.

I want FLV
Quality

Applies only when the video has to be re-encoded. A straight copy keeps the original quality.

Advanced 2
Always re-encode Rebuilds the picture as H.264 (VP9 for WebM) even when it could be copied. Fixes files that won’t play on older TVs and PCs.

Bytes of your files sent anywhere: 0 B

Related conversions

Need it the other way round? Convert FLV to MP4

Other ways to convert MP4

Convert other formats to FLV

Read more about the MP4 format and the FLV format, or see every video tool and all video conversions.

Should you convert MP4 to FLV?

Usually a quick, safe conversion. FLV can carry H.264, which is what MP4 files normally contain, so the video can often be copied across without re-encoding: fast, and with no loss at all.

Check that FLV is really needed: it plays in VLC and some streaming software; no browser or phone plays it any more, while MP4 is opens everywhere.

MP4 is the video container that plays on everything, usually holding H.264 video and AAC audio; FLV is the video format of the Flash-era web. You only need FLV for streaming software or an old system that asks for it.

MP4 and FLV compared
Property MP4 FLV
Usually contains H.264 or HEVC video with AAC audio H.264 or Sorenson Spark video with AAC or MP3 audio
Support Opens everywhere A legacy format
Plays on Every phone, browser, TV, editor, chat app and upload form VLC and some streaming software; no browser or phone plays it any more
Best for Sharing video anywhere RTMP live-streaming pipelines that still expect it
Introduced 2003 2002

How to convert MP4 to FLV

  1. 01

    Add your MP4

    Drop your MP4 video onto the box, or click to choose it. It is read from your disk and stays there.

  2. 02

    Check the settings

    The output is already set to FLV. Change the quality if you want to; the defaults suit most files.

  3. 03

    Save the FLV

    Press convert and save the FLV. Several files come back together as a ZIP.

What changes when MP4 becomes FLV

Often a straight copy

When the MP4 holds H.264 video, the stream is moved into the FLV container untouched, so the conversion takes seconds even for long files. If the codec inside is something FLV can’t hold, the picture is re-encoded instead and you’ll see a progress bar that takes longer.

FLV is an older format

You only need FLV for streaming software or an old system that asks for it. For sharing, uploading or playing on phones, MP4 is the better choice.

The size stays about the same

MP4 and FLV are close in size for the same content, so do this for compatibility rather than to save space. MP4: 1080p phone video runs roughly 60–130 MB a minute. FLV: Usually low resolution and modest size.

This page is put together from our notes on each format, choosing only what is true of MP4 and FLV, so every pairing states the same facts the same way. How these pages are made.

Why it doesn’t upload

Video files are big, and uploading one just to change its container can take longer than the conversion itself. Your browser can read and write these formats, so the file never has to leave your device.

How to check for yourself

Worth knowing

  • About the MP4. An MP4 that won’t play is rarely broken; it usually holds a newer codec such as HEVC or AV1 that the player doesn’t support.
  • About the FLV. Old FLVs often use the Sorenson Spark codec, which nothing modern decodes, so they must be re-encoded rather than just renamed.
  • MP4, MOV, MKV and WebM are handled by your browser’s own video engine, often with hardware help. AVI, WMV, FLV, MPG and the other older formats use the FFmpeg engine, a one-time 31 MB download, and are slower.

Questions

Does converting MP4 to FLV lose quality?

Not when the video can be copied, which is the case for most MP4 files: the stream moves into FLV untouched. If it has to be re-encoded, the default quality keeps the difference invisible.

Will a FLV play on my phone?

FLV a legacy format: VLC and some streaming software; no browser or phone plays it any more. VLC and mpv play FLV files.

Read more about this

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