FLV to MP4 Converter – Free Online

How to Convert FLV to MP4 Online

Drop your FLV file

Drag and drop your .flv file onto the box above, or click Choose Files. The request is already filled in: “Convert this to MP4”.

Say how, if you want

The AI assistant uses sensible defaults. To choose the resolution, frame rate or bitrate yourself, say so in the request, for example “Convert this to MP4 in 720p”.

Save your MP4 file

The assistant opens with your file and converts it on your own device; the file itself is never uploaded. When the MP4 file is ready, click Save. Prefer to set everything by hand, or batch-convert several files into a ZIP? The classic converter is one click away on this page.

Why Convert FLV to MP4?

Flash is gone, and with it every browser's ability to play FLV. Converting FLV to MP4 rescues old downloads, screencasts and web videos into a format that plays anywhere and uploads to YouTube, Drive or social media.

Most FLV files carry H.264 video with AAC or MP3 audio. The converter reads the FLV in your browser: H.264 video is copied into the MP4 unchanged when you keep the default settings, or re-encoded when you change them: by your browser's hardware video encoder, or by FFmpeg on your CPU for an FLV over 512 MB or in a browser that cannot encode AAC audio. Older FLV video is re-encoded to H.264 by FFmpeg. Nothing is uploaded.

Private by design: your FLV file is converted on your own device and never uploaded.
MP4 already asked for: the AI assistant's request says MP4, so one drop does it. Want a particular resolution, frame rate or bitrate? Just say so.
Batch friendly: the classic converter on this page takes several FLV files in one go and downloads them as a ZIP.
Free, no watermark: no sign-up, and nothing stamped on the output.

FLV vs MP4

FLV (Flash Video): FLV (Flash Video) was the streaming format of the Flash era. Modern browsers no longer play it, so FLV files usually need converting before they can be watched or edited. It is best for legacy Flash-era archives.

MP4 (MPEG-4 Part 14): MP4 is the most widely supported video container in the world. It usually carries H.264 or H.265 video with AAC audio, plays on every phone, browser, TV and editing app, and is the safest choice for sharing. It is best for sharing, social media, web playback and mobile devices.

In short: keep FLV when the priority is legacy Flash-era archives, and switch to MP4 when the file is headed for sharing, social media, web playback and mobile devices. Need a different target? The full Video Converter supports every format listed below.

FLV to MP4 FAQ

Do all FLV files convert?

FLV files with H.264, Sorenson Spark (H.263) or VP6 video are all read by the in-browser FFmpeg build. At the default settings H.264 is copied into the MP4 as is; Sorenson Spark and VP6 are re-encoded to H.264.

Will the MP4 keep the original quality?

For an H.264 FLV at the default settings, yes: the picture is copied, not re-encoded. Older codecs, or a lower resolution or bitrate, mean a re-encode; keep the resolution and a bitrate at or above the source to stay visually close to the original.

Is this FLV to MP4 converter free?

Yes. Converting FLV to MP4 on MediaConverter.io is free, with no watermark and no sign-up. The AI assistant runs on a free daily allowance of assistant credits; the classic converter on this page has no daily limit at all.

Are my FLV files uploaded to a server?

No. The conversion runs inside your browser using WebCodecs and FFmpeg compiled to WebAssembly, so your .flv file is read and converted on your own device and never uploaded, which keeps private recordings private and means there is no waiting in an upload queue. The AI assistant only sees what you type and basic facts about the file: its name, format, duration and size.

Is there a file size limit for FLV to MP4?

There is no plan or account limit, but the converter loads the whole FLV file into your browser's memory, so about 2 GB per file is the practical ceiling; larger files may fail to open. At the default settings an H.264 FLV's picture is copied as is; change the resolution, frame rate or bitrate and your browser's hardware (WebCodecs) re-encodes it (FFmpeg does, on your CPU, for an FLV over 512 MB or in a browser that cannot encode AAC audio). Older FLVs with Sorenson Spark or VP6 video cannot be decoded by the browser, so those run entirely in FFmpeg on your CPU and take noticeably longer.

Can I choose the MP4 settings myself?

Yes. Ask the AI assistant for a resolution, frame rate or bitrate in your request. Audio and subtitle track selection, the codec list and every other setting are in the classic converter, one click away on this page.

Which browsers support the FLV to MP4 converter?

It is built and tested on current desktop Chrome and Edge, which are also fastest because they expose hardware-accelerated WebCodecs video decoders. Recent Firefox and Safari releases support the same web APIs; if a file fails there, try Chrome or Edge.