Free online AVI to FLV converter

Convert AVI video to legacy-compatible FLV with FFmpeg or 101convert.com.

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How to convert avi to flv file

August 19, 2026
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Older Flash players, legacy web-publishing systems, and some media archives accept FLV but not AVI. Converting can also replace an incompatible AVI codec with H.264 video and AAC or MP3 audio, although current browsers and players generally prefer MP4.

What the AVI format is

AVI (Audio Video Interleave) is a Microsoft container based on RIFF. It can store video and audio encoded with codecs such as Motion JPEG, MPEG-4, DivX, Xvid, and uncompressed formats.

Windows capture tools, older digital cameras, screen-recording software, VirtualDub, and legacy editing systems commonly create AVI files. The .avi extension does not identify the codecs, resolution, frame rate, compression, or audio format inside the file. Check those properties with MediaInfo or ffprobe before selecting output settings.

What the FLV format is

FLV (Flash Video) is a container created for Adobe Flash playback. It can hold Sorenson Spark, VP6, or H.264 video and MP3 or AAC audio.

FLV was widely used for browser video before HTML5 video replaced Flash. Adobe ended Flash support in 2020, so FLV is now mainly appropriate for legacy Flash applications, older media servers, archival systems, or software that explicitly requires an .flv file. H.264-based FLV can be much smaller than uncompressed or lightly compressed AVI, but the container itself does not determine file size or quality.

How to convert the file

For a no-installation conversion, use the AVI-to-FLV converter on 101convert.com:

Open the AVI-to-FLV conversion tool on 101convert.com.
Select the source .avi file.
Start the conversion and wait for processing to finish.
Download the resulting .flv file and test it in the player or server that will use it.

Upload limits, processing time, and file-retention rules depend on the service. Keep the original AVI if it is the only copy of the source.

FFmpeg is the practical desktop option when repeatability, local processing, or batch conversion matters. Install FFmpeg, open a terminal in the source-file folder, and run:

ffmpeg -i input.avi -c:v libx264 -preset medium -crf 23 -c:a aac -b:a 128k -ar 44100 output.flv

This creates H.264 video with AAC audio. CRF controls quality rather than a fixed output size: lower values produce higher quality and larger files; values from about 18 to 23 are common starting points. Replace the input and output filenames as needed. FFmpeg normally retains the input frame rate; add a setting such as -r 30 only when the destination requires a fixed rate, because changing it can duplicate or discard frames.

H.264 encoders generally require even frame dimensions. If the source has an odd width or height, use:

ffmpeg -i input.avi -vf "scale=trunc(iw/2)*2:trunc(ih/2)*2" -c:v libx264 -preset medium -crf 23 -c:a aac -b:a 128k output.flv

For an older FLV implementation that does not decode H.264 or AAC, create an FLV1/Sorenson Spark-compatible video stream and MP3 audio instead:

ffmpeg -i input.avi -c:v flv -b:v 1200k -c:a libmp3lame -b:a 128k -ar 44100 legacy-output.flv

The older codec generally requires more bitrate than H.264 for comparable quality. Test a short sample before converting a large collection, because support varies among legacy players and servers.

Quality and compatibility limits

Most conversions require re-encoding because AVI may contain codecs that FLV software cannot read or because the target requires a different video and audio combination. H.264 and AAC encoding is lossy, so retain the original AVI and avoid converting an already compressed file repeatedly.

FLV may not preserve subtitles, multiple audio tracks, unusual timecode data, variable-frame-rate behavior, or all metadata. Verify duration, audio-video synchronization, resolution, audio channels, seeking, and playback in the actual destination software. If the destination does not specifically require FLV, use a modern format such as MP4 instead; Flash-based playback is obsolete and unsupported by current browsers.

AVI vs FLV: format comparison

How the AVI and FLV formats compare on the properties that matter most for this conversion.

Comparison of the AVI and FLV file formats
Property	.AVI Audio Video Interleave	.FLV Flash Video
Format type	Container	Container
Compression	Both	Both
Maximum resolution	8K and above	4K
Audio tracks	Multiple	One
Subtitles	Embedded in the file	Embedded in the file
Streaming	Partial	Partial
Opens in a web browser	No	Partial
Typical file size	Large	Small
Open standard	Partly open	Partly open
Introduced	1992	2002
Developer	Microsoft	Adobe Systems / Macromedia
MIME type	video/x-msvideo	video/x-flv

Open AVI file Open FLV file

Frequently asked questions

Is the AVI to FLV converter free?

Yes, converting AVI to FLV on 101convert.com is completely free. No registration, email address or installation is required. If you need a higher file size limit or want to convert more files at once, see our plans.

How large can my AVI file be?

You can upload AVI files up to 2000 MB and convert up to 1 files at once in a single batch.

What happens to my uploaded files?

Files are processed automatically and deleted from our servers within a few minutes after conversion. We never view or share your files.

Do I need to install any software to convert AVI to FLV?

No. The AVI to FLV conversion runs entirely online in your browser and works on Windows, Mac, Linux, Android and iPhone.

Did the conversion fail?

In most cases, the cause is an incorrect file format. Please upload a valid AVI file for this AVI to FLV conversion. Occasionally, the issue may be on our side. We analyze recurring conversion failures and disable or fix the converter if we detect a defect.

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