MP4 to FLV Converter

MP4 to FLV Converter

This tool accepts MP4 files, the most widely supported container, normally carrying H.264 with AAC. FLV is the container of the Flash era. Every browser dropped Flash in 2020, so there is almost nowhere left that plays an FLV file directly. Choose it only when one specific old system demands exactly this format. These two containers hold the same family of codecs, so the video and audio streams are copied across into the new container untouched — no decoding, no re-encoding, no further loss of quality.

How to convert MP4 to FLV

1. Select or drag MP4 files into the upload area.
2. Confirm that the requested output format is FLV.
3. Start the conversion and review the status of each file.
4. Download each result once processing has finished.

Convert several files in one batch

The interface currently accepts up to 10 files per batch. Files are processed one after another; duplicates, mislabeled files and damaged files may be skipped or reported as errors.

File size after conversion

The size stays practically the same, because exactly the same data is written into a different container. The difference lies only in the bookkeeping each container keeps. FLV holds the same codec pair as MP4, so the size lands close to it; the difference is only in the container bookkeeping.

Check the result

There is nothing to judge by eye: the video and audio data do not change. What is worth checking is that the file opens where you intend to use it and that sound stays in step with picture from beginning to end. If the source uses H.265 or AV1 instead of H.264, the target container may not be able to hold that codec and re-encoding happens anyway, even though the two containers belong to the same family.

Limits worth knowing

This tool changes the file format. It does not guarantee that every piece of metadata, every format-specific property or every embedded object survives the conversion. Keep the source file and test the result in the application where you plan to use it.

Frequently asked questions

Is FLV still worth using

Only when you have no choice. Flash ended in 2020; if the file still has to be usable later, MP4 is far safer.

Will a browser play FLV

No. No current browser plays FLV directly; you need a player installed on the machine.

How do I find out which codec is inside

Look at the file information in your player. The file extension tells you the container, not the codec inside it.

Why is this conversion so fast

Because there is no encoding step. The tool only reads the data and writes it out again, so the time depends on the size of the file and not on the length of the footage.

Is really nothing lost

Nothing, provided the target accepts the streams inside. The video and audio data are copied byte for byte.

Is my original file replaced?

No. The file on your device is left untouched.