Does converting FLV to MP4 reduce quality further?

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

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

No. By default we preserve the original resolution, aspect ratio, and frame rate from your FLV source. Only the container and, where required, the codec changes. If your source uses a codec that MP4 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 MP4 output?

The output size depends on the content and the compression characteristics of MP4 Video. In most cases the MP4 file will be in the same ballpark as your FLV 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 FLV to MP4 instead of staying with FLV?

Convert when you need the most compatible video container — MP4 Video plays on essentially everything (iOS, Android, Windows, macOS, web browsers, smart TVs, social platforms). Unless you have a specific need for another container, MP4 is the safe default.

What is the maximum FLV file size I can convert?

MegaConvert accepts FLV files up to 100 MB on the free service, which is enough for the vast majority of real-world Flash 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 FLV file safe and private when I upload it?

Yes. Your FLV 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 FLV to MP4

Free online FLV to MP4 converter. No signup required.

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Max file size: 100 MB

Why Convert FLV to MP4?

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

Converting Flash Video to MP4 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.

Flash Video has a known limitation: obsolete format since Adobe Flash Player reached end-of-life in 2020. In contrast, MP4 Video offers a key advantage: universal compatibility across all devices, browsers, and platforms. While Flash Video is commonly used for legacy web video archives and content migration, MP4 Video is better suited for web video streaming on youtube, vimeo, and social media.

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

FLV vs MP4: Format Comparison

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

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

How to Convert FLV to MP4

Follow these simple steps to convert your file in seconds.

Upload your FLV video
Choose your .flv 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 MP4 conversion
Click convert. Where the video codec is compatible with MP4 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 .mp4 file
When the conversion finishes, click the download link to save the new MP4 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 FLV to MP4

Practical advice to get the best results from this conversion.

Why this conversion is worth doing

Flash Video has a known limitation: obsolete format since Adobe Flash Player reached end-of-life in 2020. MP4 Video addresses this with a key advantage: universal compatibility across all devices, browsers, and platforms. Converting from FLV to MP4 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

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

Watch for this limitation in the MP4 output

MP4 Video has its own limitation worth understanding before you commit: patent-encumbered codecs (H.264/H.265) require licensing. After the conversion completes, open the MP4 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 FLV and MP4 Formats

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

Source 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

Target 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

Frequently Asked Questions

Common questions about converting FLV to MP4.

Related Conversions

Explore other conversions related to FLV and MP4.

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

Other conversions to MP4

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

Convert FLV to MP4

Why Convert FLV to MP4?

FLV vs MP4: Format Comparison

How to Convert FLV to MP4

Upload your FLV video

Start the MP4 conversion

Wait for the video conversion to complete

Download your .mp4 file

Tips for Converting FLV to MP4

Why this conversion is worth doing

Match the format to the actual workflow

Watch for this limitation in the MP4 output

Avoid transcoding unless necessary

Understanding FLV and MP4 Formats

Flash Video

Advantages

Limitations

Common Uses

MP4 Video

Advantages

Limitations

Common Uses

Frequently Asked Questions

Does converting FLV to MP4 reduce quality further?

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

What file size should I expect for the MP4 output?

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

What is the maximum FLV file size I can convert?

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

Related Conversions

Other conversions from FLV

Other conversions to MP4