Does converting MP4 to FLV reduce quality further?

Yes — re-encoding from one lossy format to another (MP4 Video to Flash Video) introduces a second round of compression artifacts on top of the loss already in your MP4 file. The drop is usually subtle if you use a sensible quality setting, but for archival you should always keep the original MP4 and avoid repeated lossy conversions.

Does the MP4 to FLV conversion change my video resolution or frame rate?

No. By default we preserve the original resolution, aspect ratio, and frame rate from your MP4 source. Only the container and, where required, the codec changes. If your source uses a codec that Flash Video cannot store, the video stream is re-encoded to a compatible codec while keeping the visual properties identical.

What file size should I expect for the FLV output?

The output size depends on the content and the compression characteristics of Flash Video. In most cases the FLV file will be in the same ballpark as your MP4 input, with differences driven by how each format encodes data. There is no fixed ratio — the converter does not change quality settings unless you ask it to.

When should I convert MP4 to FLV instead of staying with MP4?

Convert when the application, device, or workflow you are targeting prefers Flash Video over MP4 Video. If your current MP4 file already opens and behaves correctly everywhere you need it to, there is no benefit to converting — keep the original. The most common reasons to switch are compatibility (a tool only accepts FLV), distribution (recipients expect FLV), or feature requirements specific to Flash Video.

What is the maximum MP4 file size I can convert?

MegaConvert accepts MP4 files up to 100 MB on the free service, which is enough for the vast majority of real-world MP4 Video files. If you have a larger file (typical for high-resolution video or uncompressed audio), please contact us — we can sometimes accommodate larger uploads for legitimate use cases.

Is my MP4 file safe and private when I upload it?

Yes. Your MP4 file is uploaded over HTTPS, processed in an isolated job environment, and deleted from our servers within one hour. We do not read, index, store, or share the contents of your file. No account is required, so the upload is not associated with a personal identity. See our privacy policy for the full details.

Convert MP4 to FLV

Free online MP4 to FLV converter. No signup required.

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Max file size: 100 MB

Why Convert MP4 to FLV?

Understand when and why this conversion makes sense for your workflow.

Converting MP4 Video to Flash Video is often necessary to ensure playback compatibility across media players, operating systems, and streaming services. Video formats encode footage using different codecs, container structures, and compression techniques, each with distinct trade-offs between file size, quality, and support. From sharing videos online to preparing files for professional editing workflows, the right format makes a significant difference in how your content is experienced.

MP4 Video has a known limitation: patent-encumbered codecs (H.264/H.265) require licensing. In contrast, Flash Video offers a key advantage: compact file sizes with acceptable streaming quality. While MP4 Video is commonly used for web video streaming on youtube, vimeo, and social media, Flash Video is better suited for legacy web video archives and content migration.

With MegaConvert, you can convert MP4 to FLV online without installing software, preserving your video content accurately within the target format's specifications.

MP4 vs FLV: Format Comparison

Side-by-side comparison of the source and target formats.

Property	MP4 (Source)	FLV (Target)
Extension	.mp4	.flv
Full Name	MP4 Video	Flash Video
Compression	Lossy	Lossy
File Size	Medium	Varies
Best For	Web video streaming on YouTube, Vimeo, and so…	Legacy web video archives and content migration
Browser Support	Universal	Limited

How to Convert MP4 to FLV

Follow these simple steps to convert your file in seconds.

Upload your MP4 video
Choose your .mp4 file using the file picker or drag it into the upload area. Video uploads can take a few seconds for short clips and longer for high-resolution footage; the progress bar shows upload status separately from conversion. Files up to 100 MB are supported.
Start the FLV conversion
Click convert. Where the video codec is compatible with Flash Video, the stream is repackaged without re-encoding to preserve original quality. Where re-encoding is required, we use industry-standard codec presets that balance file size against quality. Audio tracks are converted in parallel.
Wait for the video conversion to complete
Video conversions take longer than other file types because video data is much larger. A short clip might finish in 10 seconds; a 100 MB file may take a minute or two depending on whether re-encoding is required. The progress bar shows the percentage complete.
Download your .flv file
When the conversion finishes, click the download link to save the new Flash Video file to your computer. The file is yours — no watermarks, no expiration on the file itself, and no MegaConvert account is required to download it.

Tips for Converting MP4 to FLV

Practical advice to get the best results from this conversion.

Why this conversion is worth doing

MP4 Video has a known limitation: patent-encumbered codecs (H.264/H.265) require licensing. Flash Video addresses this with a key advantage: compact file sizes with acceptable streaming quality. Converting from MP4 to FLV is most worthwhile when this specific trade-off matters for the way you intend to use the file.

Match the format to the actual workflow

MP4 Video is most commonly used for web video streaming on youtube, vimeo, and social media, while Flash Video is the standard for legacy web video archives and content migration. If your workflow is closer to the second pattern, converting makes sense. If you are still working in a context where MP4 is the norm, converting may create unnecessary compatibility friction with collaborators or tools that expect the source format.

Watch for this limitation in the FLV output

Flash Video has its own limitation worth understanding before you commit: obsolete format since Adobe Flash Player reached end-of-life in 2020. After the conversion completes, open the FLV file and verify that this limitation does not affect your specific use case — for some workflows it is irrelevant; for others it can be a deal-breaker.

Avoid transcoding unless necessary

Every time you transcode (re-encode) a video, some quality is lost unless you use a lossless codec. If you only need to change the container format without changing the codec, use a remux (stream copy) operation instead of a full re-encode. This preserves original quality and is much faster.

Understanding MP4 and FLV Formats

Learn about the source and target file formats to understand what happens during conversion.

Source Format

MP4 Video

video/mp4

MP4 (MPEG-4 Part 14) is the most widely used digital video container format, capable of storing video, audio, subtitles, and metadata. It typically contains H.264 or H.265 encoded video with AAC audio, providing an excellent balance of quality and compression. MP4 is the standard format for web video, streaming, and virtually all modern video platforms.

Advantages

Universal compatibility across all devices, browsers, and platforms
Excellent compression with H.264/H.265 codecs for high-quality video
Supports streaming, subtitles, chapters, and multiple audio tracks

Limitations

Patent-encumbered codecs (H.264/H.265) require licensing
Container flexibility can lead to codec compatibility issues
Not ideal for lossless video storage or professional editing

Common Uses

Web video streaming on YouTube, Vimeo, and social media
Smartphone and camera video recording
Digital video distribution and download

Target Format

Flash Video

video/x-flv

FLV (Flash Video) is a container format that was used to deliver video content over the internet via Adobe Flash Player. It typically contains video encoded with Sorenson Spark or VP6 codecs and audio in MP3 or AAC format. FLV was once the dominant web video format but became obsolete after major browsers discontinued Flash Player support in 2020.

Advantages

Compact file sizes with acceptable streaming quality
Simple container structure that is quick to parse
Large existing archive of legacy web video content

Limitations

Obsolete format since Adobe Flash Player reached end-of-life in 2020
No modern browser supports FLV playback without third-party tools
Limited codec support compared to modern containers like MP4

Common Uses

Legacy web video archives and content migration
Converting old Flash-based video content to modern formats
Historical video content from early streaming platforms

Frequently Asked Questions

Common questions about converting MP4 to FLV.

Related Conversions

Explore other conversions related to MP4 and FLV.

Other conversions from MP4

MP4 to AVI MP4 to MKV MP4 to MOV MP4 to WMV MP4 to WEBM MP4 to M4V MP4 to MPG MP4 to MPEG MP4 to 3GP MP4 to OGV

Other conversions to FLV

AVI to FLV MKV to FLV MOV to FLV WMV to FLV WEBM to FLV M4V to FLV MPG to FLV MPEG to FLV 3GP to FLV OGV to FLV

Convert MP4 to FLV

Why Convert MP4 to FLV?

MP4 vs FLV: Format Comparison

How to Convert MP4 to FLV

Upload your MP4 video

Start the FLV conversion

Wait for the video conversion to complete

Download your .flv file

Tips for Converting MP4 to FLV

Why this conversion is worth doing

Match the format to the actual workflow

Watch for this limitation in the FLV output

Avoid transcoding unless necessary

Understanding MP4 and FLV Formats

MP4 Video

Advantages

Limitations

Common Uses

Flash Video

Advantages

Limitations

Common Uses

Frequently Asked Questions

Does converting MP4 to FLV reduce quality further?

Does the MP4 to FLV conversion change my video resolution or frame rate?

What file size should I expect for the FLV output?

When should I convert MP4 to FLV instead of staying with MP4?

What is the maximum MP4 file size I can convert?

Is my MP4 file safe and private when I upload it?

Related Conversions

Other conversions from MP4

Other conversions to FLV