Step 1: Supply your MP4 files using the button above or by haul and lay.
Step 2: Click the 'Convert' button to start the conversion.
Step 3: Get your converted FLV files.
MP4 to FLV Conversion FAQ
What does the MP4 to FLV converter do?
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Converting modern MP4 into FLV is useful for older editing software or legacy playback hardware. The converter remuxes or re-encodes as needed; expect a larger file because legacy codecs compress less efficiently.
Will resolution and frame rate be preserved in the FLV?
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Yes. MP4 → FLV keeps resolution, frame rate, and aspect ratio unchanged by default. To change them, use the Resize or Speed tool on the result.
Is the MP4 to FLV conversion reversible?
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You can convert the FLV back to MP4 on this site. If either format involved is lossy, the round-trip is not bit-perfect even though it is visually or audibly close.
Will the converted FLV be a different size than the MP4?
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Modern codecs compress better, so FLV from a legacy MP4 is typically 30-60% smaller at equivalent quality. Conversions in the opposite direction can grow the file.
What happens to the subtitle tracks in my MP4 file?
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They cannot stay selectable, because FLV has no soft-subtitle stream to hold them. There are two ways out: burn them into the video during conversion, which makes them permanent and unstyleable, or export them as a separate .srt alongside the FLV for the player to load. The converter tells you which it did rather than dropping them silently. No current browser, phone or TV can play FLV — anything still in this container has to be moved out of it to remain watchable.
Can I still embed the file on a web page after converting MP4 to FLV?
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Not directly. MP4 plays inline in every browser; FLV does not, so a page embedding it falls back to a download link or an empty player frame. If the file is destined for a website, keep the MP4 for the web and treat the FLV as the archive or editing copy.
Will the FLV still play smoothly on a phone or a TV?
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It may not. MP4 is decoded by dedicated silicon on phones, tablets and TVs, which is why it plays without flattening the battery. FLV typically falls back to software decoding on the same hardware — higher CPU load, a warmer device, and dropped frames on 4K material. For a device target, MP4 is the safer container to stay in.
What happens to 5.1 surround audio when converting MP4 to FLV?
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It is downmixed to stereo, because FLV has no dependable multichannel path. The fold-down uses the standard ITU coefficients so dialogue in the centre channel stays intelligible and the surrounds come in at reduced level rather than vanishing. Anything that relied on discrete channel placement is gone after that.
Why would I convert MP4 to an older format like FLV?
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Because a lot of hardware never learned anything newer and never will. DVD players, in-car head units, camcorder playback modes, industrial displays and plenty of broadcast ingest equipment accept FLV and nothing else. The conversion is a deliberate step down in efficiency, bought in exchange for working on a device that has no other option. FLV’s low per-packet overhead made it excellent at streaming over the unreliable connections of its era, and huge archives of it still exist.
Is there a file-size limit when converting MP4 to FLV?
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Anonymous uploads are capped at a generous default; signed-in free accounts get a higher cap, and Pro accounts have no per-file limit. Browser memory is usually the practical constraint long before our server-side limits kick in.
Can I batch-convert several MP4 files to FLV at once?
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Yes. Drop or pick multiple MP4 files in one upload — the converter processes them in parallel and returns a ZIP of the FLV results. There is no need to repeat the upload step per file.
What happens to my MP4 files after the conversion?
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Uploaded files and FLV outputs are auto-deleted after a short retention window. We do not inspect, share, or train on user files. Direct download links are time-limited and tied to your session.
