FLV to MP4 Converter

Bring old Flash video into the modern day. Convert FLV to MP4 free in your browser, with no signup, no file limits, and no watermark.

Select FLV file →

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Click or drag and drop to upload files

We support most file types including: MP4, MOV, WEBM, AVI, MP3, WAV, PNG, JPEG, GIF, MKV, PDF, FLAC, TIFF!

EchoWave is used by creators, marketers, educators, and businesses to convert and edit media online.

Updated June 2026

FLV is Adobe Flash video, and since browsers dropped Flash support at the end of 2020 those files are awkward to play. Converting FLV to MP4 fixes that: MP4 is the format phones, browsers, TVs, and editors all understand. Many FLV files already hold H.264 video, which is exactly what MP4 expects, so the change is often quick and keeps the picture sharp.

Free, no sign-upNo account, no trial

Runs in your browserNothing to install

Works on every devicePhone, tablet, laptop

No watermarkClean output, every time

How it works

How to convert FLV to MP4

1
Upload your FLV
Drag your FLV onto the converter or pick it from your device. Nothing to install.
2
Choose MP4 and convert
Select MP4 as the output and start. Free, with no sign-up and no watermark.
3
Download your MP4
Save the finished MP4, or open it in the editor to trim, crop, or resize it first.

Try it

Estimate your MP4

Pick a video bitrate and a length to see the MP4 file size before you convert.

Video bitrate

Length5 min

1 min30 min

Estimated MP4 size183MBSharp 1080p

An estimate. Real size varies with resolution, frame rate, and how much the picture moves.

The formats

FLV vs MP4

FLV

Flash Video

Legacy Flash video from the pre-HTML5 web

Type: Flash video container
Holds: H.263, VP6, or H.264 video with MP3 or AAC audio
Typical size: Small, made for streaming
Plays on: VLC, since browsers dropped Flash in 2020

Best for:Recovering old Flash web video

MP4

MPEG-4 Part 14

The video format that plays everywhere

Type: Video container
Holds: H.264 video plus AAC audio, sometimes subtitles
Typical size: Large, it carries video
Plays on: Phones, browsers, TVs, almost any player

Best for:Watching and sharing video

Will it lose quality?

When the codecs already match MP4, the converter can change the container without re-encoding, so the picture stays identical.
When the video has to be re-encoded for MP4, a high bitrate keeps it visually close to the FLV.
Converting cannot add detail the FLV never had. The output is at best as good as the source.

Use cases

What people use it for

Play anywhereMake a clip your device supports

Video editorsGet footage your software accepts

Web videoUse a format browsers play

CourseworkHand in a standard video file

SharingSend a clip people can open

Troubleshooting

If something looks off

The MP4 will not play

Some players are picky about codecs. Try it in VLC, which opens almost anything, or convert again and let the converter re-encode the video.

The file got larger

A format change can shift the size, and re-encoding at a high bitrate adds overhead. Lower the bitrate or trim the clip for a smaller file.

Audio and video drift out of sync

Re-download the source and convert again. If a long recording drifts, splitting it into shorter pieces usually fixes the sync.

FAQ

FLV to MP4 questions

Why convert FLV to MP4?

Flash Player was retired in 2020, so FLV no longer plays in browsers and most phones cannot open it. MP4 plays almost everywhere, uploads cleanly to YouTube and social sites, and imports into nearly every editor, which makes it the practical home for old Flash video.

Is the FLV to MP4 converter free?

Yes. EchoWave converts FLV to MP4 with no signup, no file-count limit, no trial, and no watermark. Upload your FLV, convert it, and download the MP4 from your browser.

How do I convert FLV to MP4?

Upload your FLV, choose MP4 as the output format, and start the conversion. When it finishes, download the MP4 or open it in the editor to trim, crop, or add captions.

Will converting FLV to MP4 lower the quality?

Many FLV files already use H.264 video, which MP4 supports, so the converter can often change the container with little or no re-encoding and keep the picture as it was. When a re-encode is needed, a high bitrate keeps the result close to the source. Converting cannot add detail the FLV never had.

Does the FLV to MP4 converter work on Mac, Windows, iPhone, and Android?

Yes. The converter runs in any browser, so it works on macOS, Windows, Chromebook, Linux, iPhone, iPad, and Android with nothing to install. The MP4 you get back plays natively on all of them.

Why does my FLV not play in QuickTime or Windows Media Player?

Those players never fully supported the Flash container, and Flash itself is gone. Converting to MP4 gives you a file QuickTime, Windows Media Player, and the default apps on your phone open without any extra plugin.

The converted MP4 has no sound. What happened?

Some FLV files store audio in older codecs that not every player handles. The converter still extracts the track, but if a clip plays silent, re-download the original FLV and convert it again so the audio stream comes through cleanly.

Can I convert large FLV files or several recordings?

Yes. There are no file-count limits on these pages, so you can convert your Flash videos one after another. Large files are supported and simply take a little longer to upload and convert.

Can I edit the video while converting it?

Yes. Open your file in the editor to trim out dead air, crop the frame, or add subtitles before you export the MP4, so you only keep the part you actually need.