CONVERT
FLV → AVI
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Fast, secure FLV to AVI conversion. No registration required.
FLV (Flash Video) was Flash Player's native container, built around Sorenson Spark or On2 VP6 video codecs and MP3 or AAC audio. Both codecs are intra- and inter-frame compressed with lossy DCT, which means the encoded bitstream already discards perceptual information before you touch it. AVI (Audio Video Interleave) is Microsoft's RIFF-based container from 1992 — it wraps nearly any codec, imposes no container-level compression of its own, and is universally read by Windows Media Player, VLC, video editing suites from Premiere to DaVinci Resolve, and virtually every NLE released in the last two decades. The conversion from FLV to AVI is a re-mux combined with a transcode: the video stream is decoded from VP6 or Sorenson Spark and re-encoded, most commonly into H.264 (AVC) or MPEG-4 Part 2 inside the AVI wrapper, and the audio is decoded and re-encoded from MP3 or AAC into MP3 or PCM. Because FLV carries no chapter markers, no subtitle tracks, and no embedded thumbnail standard, nothing structural is lost in that sense — the container was already sparse. What matters is the codec transcode chain and whether the encoder settings match or exceed the source bitrate.
Flash Video
Source formatFLV was the dominant web video format during the Flash era. While Flash is now deprecated, many legacy video files still exist in FLV format and need conversion to modern formats.
AVI Video
Target formatAVI is a legacy Microsoft multimedia container that stores audio and video data. While largely superseded by modern formats, it remains widely recognized and is produced by many older devices and screen recorders.
Why convert FLV to AVI
FLV stopped being deliverable the moment Adobe dropped Flash in 2020. No modern browser plays FLV natively, iOS and Android never supported it, and Windows 10 and 11 do not include a Flash codec pack. Users convert FLV to AVI specifically to feed the file into Windows-native workflows: video editors that accept AVI with H.264 or MPEG-4, DVD authoring tools, and older capture or playback hardware whose firmware predates MP4 support. AVI with a widely supported codec is the path of least resistance for anything in the Windows editing ecosystem that predates 2015.
HOW TO CONVERT
FLV → AVI
Drop the video file
Select a FLV file. We read the container and stream descriptors to plan the conversion.
FFmpeg handles the repackage
When codecs align, FFmpeg rewraps the existing streams into a AVI container — no quality loss, near-instant finish.
Retrieve the AVI
The AVI download is ready in seconds for stream-copy jobs, minutes for full transcodes.
Common Use Cases
Share across platforms
Send AVI files to anyone without worrying about whether they have the right software for FLV.
Embed in documents
Drop AVI output into Word, Google Docs, PowerPoint, Notion or a website without conversion warnings.
Optimize size
AVI often produces smaller files than FLV for web, email and storage.
Archive & future-proof
Store in a widely-supported format that will still open on future operating systems without legacy plugins.
FLV vs AVI — Strengths and limitations
What each format does best, and where it falls short.
FLV Strengths
- Low overhead — the container is extremely compact.
- Designed for streaming — progressive download and seeking work well.
- Decoded natively by Flash Player on every OS for 20 years.
Limitations
- Flash Player is dead — no modern browser can play FLV without conversion.
- Legacy codecs (Sorenson, VP6) are poorly supported in modern tooling.
- Hardware video decoders never added FLV support.
AVI Strengths
- Simple, well-documented format — trivial for any video library to parse.
- Universal Windows playback since Video for Windows in 1992.
- Low encoding overhead — interleaved structure is fast to write.
- Works with any codec technically, including modern ones.
Limitations
- Aging container — no native support for chapters, subtitles, or multi-audio selection.
- File-size limits (2 GB original, 4 GB with OpenDML) break for HD content.
- Variable-framerate video causes sync drift.
FLV vs AVI — Technical specifications
Side-by-side comparison of the technical details.
FLV
- MIME type
- video/x-flv
- Extensions
- .flv, .f4v
- Video codecs
- Sorenson Spark, VP6, H.264 (F4V)
- Audio codecs
- MP3, Nellymoser, AAC
- Status
- Deprecated since December 31, 2020
AVI
- MIME type
- video/x-msvideo
- Extension
- .avi
- Container
- RIFF
- Max file size
- 2 GB (original); 4 GB (OpenDML extension)
- Codec support
- Any codec via FourCC identifiers
| Specification | FLV | AVI |
|---|---|---|
| MIME type | video/x-flv | video/x-msvideo |
| Extensions | .flv, .f4v | — |
| Video codecs | Sorenson Spark, VP6, H.264 (F4V) | — |
| Audio codecs | MP3, Nellymoser, AAC | — |
| Status | Deprecated since December 31, 2020 | — |
| Extension | — | .avi |
| Container | — | RIFF |
| Max file size | — | 2 GB (original); 4 GB (OpenDML extension) |
| Codec support | — | Any codec via FourCC identifiers |
FLV vs AVI — Typical file sizes
Approximate file sizes for common scenarios.
FLV
- 10-min YouTube 2008-era video 40-80 MB
- 45-min TV show (FLV H.264) 200-500 MB
AVI
- 10-min video (XviD / MP3) 100-200 MB
- 45-min TV episode (DivX) 350-700 MB
- 2-hour movie (DVD rip) 700 MB - 1.4 GB
Quality & Compatibility
FLV carries no alpha channel — VP6-E had an alpha variant used exclusively by Flash for compositing, but standard FLV files distributed for playback carry opaque video only, so no transparency is lost. Color space is YCbCr 4:2:0 at 8 bits per channel in virtually all FLV sources; AVI with H.264 preserves that color space identically. The critical quality trade-off is the transcode: decoding VP6 or Sorenson Spark and re-encoding to H.264 inside AVI is a generation loss. At equivalent bitrates the output quality will be slightly below the original encode. Metadata support in AVI is limited to basic tags; FLV's onMetaData event data (duration, framerate hints, creation date) does not map to AVI atoms and is dropped. No subtitle or chapter data survives because FLV carries none to begin with.
Tips for Best Results
- Match or slightly exceed the source bitrate when re-encoding to H.264 inside AVI — FLV files encoded at, say, 800 kbps video should target 900–1000 kbps to absorb the generation loss without visible macroblocking.
- If the source FLV uses On2 VP6 with an interlaced flag (rare but present in some broadcast-captured FLV), check whether the output player expects progressive frames — AVI does not carry a mandatory deinterlace signal, so forcing progressive encoding at conversion time avoids comb artifacts in playback.
- AVI has a practical file size ceiling near 2 GB under the original RIFF spec; files above that require the OpenDML (AVI 2.0) extension, which most modern players support but some embedded or legacy hardware does not — keep this in mind for long FLV recordings at high bitrate.
Frequently Asked Questions
Only when it has to. If the codecs inside FLV (usually H.264 or H.265 for video, AAC for audio) are accepted by AVI, we stream-copy — the bytes are repackaged into the new container with zero re-encoding and no quality loss. When the source uses a codec the target does not support, we transcode at a matching bitrate to keep the visual quality close to the original.
With stream copy, expect the job to finish in seconds to tens of seconds regardless of video length — the work is mostly rewriting the container. Transcoding is slower (roughly real-time: a ten-minute clip takes about ten minutes) because every frame must be decoded and re-encoded. The progress bar shows which mode applies.
Yes. Resolution, frame rate, colour space and bit depth are preserved by default; stream copy is literally bit-identical on these parameters. If you explicitly pick a lower bitrate or a different codec in Advanced, the output is rebuilt to those settings, but the default is always "match the source".
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Read guideSecure & Private Conversion
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