Convert AVI to FLV Audio Video Interleave ↔ Flash Video Free Online Secure
Your AVI is opened here in your browser and written out as FLV. That container accepts only a few codecs, and an ordinary DivX AVI is not one of them — so the picture is usually re-encoded, which takes longer than a plain rewrite.
Convert your file
Drop an AVI here, or choose one.
Your file never leaves this device. Everything runs in your browser.
Nothing uploaded
Where these formats come from
AVI is Microsoft's container from 1992, built when video was something you played from a CD-ROM. MOV is Apple's, a year older, and it was so well designed that the MP4 format the whole world now uses was built directly on it. FLV was Macromedia's, later Adobe's: it carried almost all internet video for a decade and disappeared with Flash at the end of 2020. The word that matters here is container. None of these three is a way of compressing video; each is a box that holds video compressed by something else, alongside the sound and the subtitles. That distinction explains most of the surprises on this page.
Where you meet them
AVI survives in old camera footage, in archives and in software that was written in the nineties and never replaced. MOV comes out of iPhones and Macs and is the working format of a great deal of video editing. FLV is almost entirely a legacy: files downloaded or recorded before 2020 that nothing modern will open. Converting between them is usually about making an old recording playable again, or handing a file to a program that insists on one particular box.
Questions people ask
What is the difference between a container and a codec?
The container is the box — AVI, MOV, MP4 — and the codec is how the pictures inside were compressed — H.264, MPEG-4, and others. A file called .avi tells you almost nothing about what is inside it. This is why one AVI plays and another does not, although both have the same extension: the player understands the box but not the codec within. It is also why converting between containers is sometimes instant and sometimes slow — in the first case only the box is being changed.
Why won't my old FLV files play any more?
Because the software that played them was Flash, and Flash was switched off at the end of 2020 and removed from every browser. The files themselves are intact; what has gone is the thing that knew how to open them. Converting to a modern container is the way to get them back, and it is worth doing before the tools that still understand FLV become scarce as well.
Does the file lose quality?
It depends on what the two formats can hold. Converting between formats that store the same thing — a PNG to a BMP, a WAV to a FLAC — loses nothing. Converting into a format that throws information away to save space, such as JPEG or MP3, loses a little every time, and converting back does not bring it back. Where a choice exists, this page errs towards keeping the original quality rather than making the smallest file.
Is my file uploaded anywhere?
No. The conversion happens inside your browser, on your own machine; the file never leaves it and there is no server here that could receive it. That is why a large file is limited by your own memory rather than by an upload, and why nothing you convert can appear in anybody's logs — including ours. The audio and video tools do fetch their conversion engine from this site the first time you use them, some thirty megabytes once; after that the work still happens entirely on your machine.
Why people convert AVI to FLV
This conversion runs against the current. AVI is a long-standing, widely supported video format; FLV is the format of the Flash era, which ended in 2020. Most people want to move away from FLV, not towards it. And yet the need to convert AVI to FLV still comes up, for a small number of very specific reasons. A website built years ago that still accepts only FLV uploads. A piece of software, a training system or a kiosk that was designed around Flash and cannot be changed. An archive that must stay consistent with older material. If nothing is forcing you into FLV, this page will tell you honestly that you probably do not need it.
If something does require it, the job is simple to describe: take an AVI and write it out as FLV. The difficulty lies in what that involves, because FLV accepts only a few ways of storing video, and a typical AVI does not use any of them. That is why this conversion is slower and less clean than most of the others on this site, and why this page spends some time explaining it.
This page converts AVI to FLV in your browser. Your video is not uploaded to a server, which matters for family footage and unreleased material. Below you will find how the conversion works, why the picture is usually re-encoded, why the result is often larger and poorer than the original, and what to know about the converter itself.
How the conversion works
Why the picture is usually re-encoded
A video file has two layers: inside are the picture and the sound, each compressed in a particular way; around them is a container, such as AVI or FLV. Some conversions only move the contents into a new container, which is quick and loses nothing. But FLV accepts only a few ways of compressing the picture, and an ordinary AVI, one made with the common DivX method, is not among them. So the picture usually has to be re-encoded, which means decoded and compressed again in a way FLV accepts. That takes longer than a plain rewrite.
When the picture can pass untouched
Occasionally an AVI already holds something that FLV accepts. In that case the video is moved across untouched, with no re-encoding and no loss. You will notice because the job takes seconds, not minutes. But for the typical AVI, expect a re-encode.
How to tell what happened
A conversion that takes a few seconds for a long film was a plain move. One that takes minutes and keeps the processor busy was a re-encode. Another sign is the file size: a plain move gives a file about the same size as the original, while a re-encode can change it noticeably.
What is kept
Length, frame size and sound
When you convert AVI to FLV here, the full length, the frame size and the sound are kept. A clip of five minutes stays five minutes, a picture of 640 by 480 stays 640 by 480, and the sound keeps its place. Nothing is cut or sped up.
Untouched video where possible
Where the AVI already holds something FLV accepts, the video is moved across untouched. That is the best case: no re-encoding, no loss and a quick result.
What is lost, and why the result can disappoint
Re-encoding costs a little quality
Every re-encode discards some detail, because compressing a picture means throwing information away. You are applying that to a video that has already been compressed once, so the loss adds up. In scenes with fine detail or fast movement, it can show as blockiness or smearing.
FLV's own codec is old
There is a second problem. The compression method FLV uses for pictures is old, designed for the slow connections and small screens of the early web. It needs more data than modern methods to look as good. The consequence is that the result is usually a larger file holding a poorer picture than the AVI had. You pay twice: in size and in quality.
A rough expectation
An AVI of 100 megabytes may become an FLV of 120 to 150, with a visibly softer picture, especially in busy scenes. The exact figures depend on the film, but the direction is almost certain: you will not save space and you will not gain quality.
FLV is a dead format
Flash was withdrawn in 2020, and almost nothing plays FLV now. Browsers no longer run it, and modern players include it only by courtesy, if at all. So convert to FLV only when something specifically demands it. For any other destination, it is a mistake, and you would do better to keep the AVI or move to a living format such as MOV.
What to know about the converter
It is fetched the first time
The converter itself is fetched the first time you use one of these video pages, about nine megabytes, once. After that it stays in your browser, and later conversions start straight away. On a slow connection, the first use takes longer, and offline you need to have loaded it once before.
Long films on phones
Everything runs on your own device, so a long film on a phone may run out of memory before it finishes, particularly during a re-encode. Try on a computer, or cut the video into shorter parts first.
What AVI and FLV are
AVI is a container from the early 1990s that has outlived most of its contemporaries. It can hold many kinds of picture and sound, which is both its strength and its weakness: you can open an AVI almost anywhere, but you cannot be sure what is inside it without looking. The most common content of AVI files today is DivX or Xvid video, popular in the early 2000s. FLV is a container built for Flash, designed to stream video through a browser plug-in, and it accepts only a short list of codecs, among them an old one made for Flash itself.
That difference of design explains everything about this conversion. A container that is permissive, like AVI, and one that is picky, like FLV, do not swap contents easily. The picky one demands that the picture be in one of its few accepted forms. When it is not, the picture must be converted, and conversion of video means re-encoding. When you convert AVI to FLV, you are asking the converter to satisfy a demanding destination.
Why FLV exists at all
FLV came about because Flash needed a format that could start playing before the whole file had arrived. That was a great advance in the days of slow connections, and it made online video possible for millions. Its job done, and its technology overtaken, it has faded away together with Flash. Understanding that history helps explain why the format is so dated and why you should use it only if you must.
Where FLV is still needed
It would be wrong to say nobody needs FLV any more. Some corporate training portals built in the 2000s still use it. Some museums, kiosks and exhibition systems run Flash-based players from that period and have never been replaced. Some archives follow a convention of keeping everything in one format, and for collections begun in FLV, new material must match. Some people use old devices, such as certain digital photo frames or media boxes, that read FLV.
If you are in one of these situations, you will know it, because the system will refuse any other format. In that case, convert AVI to FLV, check that the result plays in the target system and keep the AVI as the original. If you are not in one of these situations, look for an alternative format before you proceed.
Asking the right question
Before converting, ask the person or the system that requires FLV whether it would accept something else, such as MP4 or MOV. Many requirements are written from habit, and the system may in fact be able to take a modern format. A two-minute question can save you from making a larger, softer file.
Getting the best FLV you can
If you must produce an FLV, a few habits improve the outcome. Start from the best AVI you have: a re-encode of a re-encode compounds loss. Trim the video to what is needed before converting, so you are not re-encoding material nobody will see. And keep the picture size no bigger than the destination requires, since a smaller picture is cheaper to re-encode and shows fewer defects.
Then judge the result by looking at the scenes that are hardest on compression: fast movement, fine texture, smoke, water and dark areas with subtle gradations. If those look acceptable, the rest will. If they look blocky or smeared, there is little you can do with FLV's old codec; the limitation is the format, not the converter.
Audio
The sound is usually the easy part. It is moved or converted without noticeable loss, and stays in step with the picture. If the audio matters on its own, such as music, keep the original AVI as the source for any other use.
How to convert AVI to FLV here
First, ask whether you need FLV
Find out what requires FLV: a website, a program or a person. If it accepts another format, use that instead. If FLV is truly required, go ahead.
Add your video
Drop the AVI onto the page or pick it from your device. It is opened inside your browser and is not uploaded.
Let it finish and check
Press the button and leave the page open. Because the picture is usually re-encoded, it takes longer than a simple rewrite. Download the FLV and play it in the program or on the site where it is needed. Keep the AVI: it is the better file.
Questions people ask before converting
Why is it slow?
Because the picture is usually re-encoded, frame by frame. A plain rewrite takes seconds; a re-encode takes much longer.
Why is the FLV bigger than the AVI?
Because FLV's own codec is old and needs more data for the same picture. A larger file is normal.
Can I make the FLV smaller?
Not through this page. If size matters, a different format would serve better, but then you are no longer making an FLV.
Will it play on a modern player?
Not necessarily. Flash was withdrawn, and many players no longer read FLV. For modern playback, keep the AVI or use MOV.
Is my video uploaded?
No. Everything runs in your browser and the video never leaves your device.
Who converts AVI to FLV
People maintaining old sites and systems
A legacy website or training system that only takes FLV leaves no choice.
Archivists matching older collections
Where a collection was built in FLV and must stay consistent, new items are converted to match.
Users of equipment from the Flash era
A few devices made before 2020 read FLV. Converting lets you put a video on them.
Common mistakes
Converting to FLV to save space
FLV is not a small format. The file usually grows. If you want a smaller file, FLV is not the answer.
Deleting the AVI
Keep it. It is the original and the better file.
Converting in chains
Each re-encode costs quality. Convert once, from the original.
Related tools
To go the other way, convert FLV to AVI, which is usually quick and lossless. For Apple's format, AVI to MOV, MOV to AVI, FLV to MOV and MOV to FLV work the same way. For the soundtrack alone, WAV to MP3 and M4A to MP3 change the audio format.
When to convert AVI to FLV, and when not to
You should convert AVI to FLV only when a site, a program or a device demands FLV and accepts nothing else. It is the wrong move for sharing, for archiving or for playing on a modern device, because the file is usually larger and the picture poorer than the AVI. If a destination accepts MP4 or MOV, use those. When you do convert AVI to FLV, do it once, from the original, and keep the AVI.
For the few cases where you must, it is private and straightforward to convert AVI to FLV in the browser. Your original is never changed, so you can come back and convert AVI to FLV again from the original whenever you like. If the result is rejected by the target system, check which codec it expects: the converter writes the standard one, but some old systems are fussy.
A routine to convert AVI to FLV with the least damage
Confirm that FLV is required. Take the best AVI you have and trim it to what is needed. Convert AVI to FLV, leave the page open until the download is ready and play the result in the target system. Watch the hardest scenes. If it is acceptable, keep the FLV for that system and the AVI for everything else. When you convert AVI to FLV in a batch, try one first and check it, so you do not discover a problem after twenty files.
Checking the result properly
After you convert AVI to FLV, play the FLV from the beginning, jump to the middle and watch the end. Check that sound and picture stay together, that the length matches and that the picture is acceptable. If something is wrong, the AVI is untouched, so you can convert AVI to FLV again, or look at converting from MOV if that was your original format.
Related destinations
If the real aim is to open the video on an Apple device, converting AVI to MOV is a far better route than FLV: it usually moves the contents untouched, so nothing is lost. For a film that is already in FLV and needs rescuing, FLV to AVI goes the opposite way and is typically quick and lossless.
Your video stays on your device
The conversion happens locally. Your video is opened by your own browser, re-encoded or moved there and handed back. Nothing is uploaded, so there is no copy on a server and no one else who could watch it. For family footage and private recordings, that is the safe way to convert AVI to FLV.
A worked example
Say you maintain an old training portal that accepts only FLV, and a colleague sends you a five-minute demonstration as an AVI of 60 megabytes. You drop it here and press the button. The converter re-encodes the picture, which takes a couple of minutes, and you download an FLV of about 80 megabytes, with the same length and sound but a slightly softer picture. You upload it to the portal, where it plays. The AVI stays on your computer as the better original.
Before you close the page
Check that you downloaded the FLV, that it plays where it is needed, and that you kept the original AVI.
Summary
To convert AVI to FLV here, drop the video and press the button. The full length, the frame size and the sound are kept, and where the AVI already holds something FLV accepts, the video is moved across untouched. Usually, however, the picture is re-encoded, which costs a little quality, and FLV's own codec is old, so the result is typically a larger file with a poorer picture. FLV is a dead format: convert to it only when something demands it. Nothing leaves your device.