Why can't I play FLV files anymore?

FLV files required Adobe Flash Player, which was officially discontinued on December 31, 2020. All major browsers have removed Flash support entirely, making FLV files unplayable without conversion.

Will the quality of my old FLV videos be preserved?

The converter preserves whatever quality exists in the original FLV file. Keep in mind that many FLV files were encoded at lower bitrates typical of early web video, so the source quality may be limited.

Can I convert FLV files from old websites I downloaded?

Yes. Any FLV file you have saved locally can be converted, regardless of where it originally came from. The converter processes the file directly in your browser.

What codecs do FLV files contain?

FLV files typically contain Sorenson Spark (H.263) or VP6 video with MP3 audio. Some later FLV files may contain H.264 video, which can be remuxed to MP4 with no quality loss.

Is there a batch conversion option for multiple FLV files?

You can convert files one at a time through the converter. For large FLV archives, convert each file individually to ensure the best quality output.

FLV to MP4 Converter

Adobe Flash was discontinued in 2020, leaving millions of FLV video files unplayable in modern browsers and devices. Converting FLV to MP4 rescues your Flash Video content and makes it playable everywhere, from smartphones and smart TVs to social media platforms and modern web browsers.

100% Private — Your files never leave your device

Convert MP4 to FLV instead

FLV files typically use older codecs like Sorenson Spark or VP6, which are less efficient than modern H.264. The conversion to MP4 preserves the original quality level, but the source video may already be lower quality due to the compression standards of the Flash era.

How to Convert FLV to MP4

1
Upload your FLV file by dragging it into the converter or clicking the upload button.
2
Confirm MP4 as the output format.
3
Click Convert and download your rescued MP4 file once processing completes.

FLV vs MP4 — Format Comparison

Feature	FLV	MP4
Full Name	Flash Video	MPEG-4 Part 14
Type	Video	Video
Codec	Sorenson Spark / H.264 / VP6	H.264 / H.265 / AV1
Lossless	No	No
Extension	.flv	.mp4
Best For	Legacy web video archives	Online video streaming

FLV Strengths

Very small file sizes
Fast streaming performance
Widely used in legacy video archives

MP4 Strengths

Universal device and browser support
Excellent compression-to-quality ratio
Supports subtitles, chapters, and metadata

Frequently Asked Questions

When to Convert FLV to MP4

Rescuing Flash-era video content before it becomes permanently inaccessible
Converting downloaded FLV videos from old websites into a modern format
Migrating legacy e-learning or training video libraries from FLV to MP4
Preserving historical web video content in a future-proof format

Related Conversions

FLVMOV FLVAVI FLVMKV FLVWebM MOVMP4 AVIMP4 MKVMP4 WebMMP4

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About Our FLV to MP4 Converter

This converter uses FFmpeg compiled to WebAssembly (WASM) to transform your FLV files into MP4 format entirely inside your web browser. When you select a file for conversion, the processing happens locally on your device. Your file is never uploaded to any server, never transmitted over the internet, and never stored anywhere outside your own computer. This privacy-first architecture makes our tool safe for confidential and sensitive content — including legal recordings, medical files, financial presentations, personal media, and any other material you would not want on a third-party server.

The conversion process works by decoding the FLV input using FFmpeg's highly optimized decoders, then encoding the output in MP4 format with carefully tuned settings that balance quality and file size. When possible, the tool uses stream copy mode to remux (rewrap) compatible streams without re-encoding, which preserves the original quality with zero generational loss. When re-encoding is necessary due to codec differences between the two formats, the converter uses high-quality encoding settings to minimize any visible or audible quality reduction.

Supported input formats include MP4, MOV, AVI, MKV, and WebM for video, with automatic detection of the codecs and parameters inside your source file. The output is optimized for maximum compatibility with modern devices and platforms including Windows, macOS, Linux, iOS, Android, smart TVs, and all major web browsers.

Why browser-based conversion is safer: traditional online converters require you to upload your file to a remote server, where it is processed by third-party infrastructure and then made available for download. This workflow exposes your data to interception during upload, unauthorized access on the server, unclear data retention policies, and potential data breaches. Professionals in regulated industries such as healthcare (HIPAA), legal (attorney-client privilege), and finance (SOX, GDPR) often cannot use server-based converters without violating compliance requirements. Our WebAssembly-powered approach eliminates all of these risks by ensuring your data never leaves the browser sandbox on your own device.

The tool handles files up to 500 MB on desktop browsers and 200 MB on mobile devices. No account registration, no software installation, and no recurring subscription is required. Conversion typically completes in seconds for small files and a few minutes for larger ones, depending on your device's processing capabilities. Once the conversion is finished, you can download the result immediately and the source data is discarded from browser memory.