1Upload every file you want combined — at least two of them.
2Drag the uploaded items into the order you want; the order is taken from the list, not from the filenames.
3Start the merge, which joins matching inputs without re-encoding them and reconciles mismatched ones exactly once.
4Download the single combined FLV file.
Merge FLV FAQ
Does it matter if the inputs are different formats?
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It does. FLV is the retired Flash container — nothing plays it natively any more, which is normally the reason it is being converted. Matching inputs take a fast, lossless path; mismatched ones have to be reconciled to a common format, which is slower and costs one encode.
Anything specific to FLV when merging?
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Yes — nothing plays FLV natively any more, so the practical end of any FLV job is a modern container. That is worth checking when the inputs did not all come from the same source.
How does Merge FLV join the files together?
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Concretely, clips with matching codec, resolution and frame rate are concatenated as a stream copy and the join is instant; anything mismatched is normalised to a common format first, which is the slow path but the only correct one. Upload everything you want combined and the result comes back as a single file.
Can I control the order things are joined in?
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Yes — drag the uploaded items into the order you want before starting. Order is taken from the list, not from the filenames, so "IMG_2.jpg" sorting after "IMG_10.jpg" is not a problem you have to solve first.
What happens to audio, subtitle and chapter tracks?
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They are carried across. Multi-track audio, embedded subtitle tracks and chapter markers survive wherever the target container can represent them — that is the main thing that separates a proper job from a naive re-encode that silently keeps only track one.
What can I upload to Merge FLV?
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MP4, MOV, MKV, WebM, AVI, WMV, FLV, 3GP, M4V, MPEG and MPG. The container and codec are probed before anything runs, so a mixed batch is handled correctly per file rather than assumed to be uniform.
Is there a file size limit on Merge FLV?
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Yes: free accounts process video up to 1 GiB per file, by far the most generous cap on the site; ffmpeg with x264, x265 and libvpx does the work, which is the same toolchain behind most desktop video software. Video is the one family where the cap is high enough that upload time, not the limit, is what you will actually notice.
Will Merge FLV lower the quality of my FLV videos?
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It depends on whether the job needs a re-encode. Operations that only touch the container or the timeline are done as a stream copy and the picture is bit-identical to the source. Anything that has to redraw frames goes through x264/x265 at a quality level you set, where CRF 23 is visually transparent on most footage.
Why would a modern-format site run Merge FLV?
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WEBP.to is built around the modern replacement for both of the old defaults: one format that does lossy, lossless, alpha and animation, and reliably lands smaller than the JPEG or PNG it came from. People arrive here having decided the old defaults are costing them bandwidth, and that decision immediately raises the rest: what size, what quality, what happens to the transparency. Merge FLV is on the same upload and the same account so those questions get answered in one place.
Once Merge FLV has run, what is worth doing next?
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The converter on this site moves images to and from WebP, PNG, JPG and AVIF, which is where you decide whether a smaller file is worth losing the older browsers. Doing it in that order matters: pick the pixels first and the container afterwards, because the container is the cheap decision and the pixels are the expensive one.
Do the sibling sites run something different?
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The engines are identical — same libraries, same workers, same caps. What is different is the opinion attached, and the opinion here rests on a property of the format this site is named after: the same .webp extension can hold a lossy VP8 frame, a lossless one, or an animation, so the sensible processing path is decided per file rather than per extension.
What happens to my file, and is an account required?
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No account, and nothing is retained: uploads are deleted from the workers shortly after the job finishes, and nothing is inspected, listed or indexed. Accounts exist for history and batch size only.
