Video Format Comparison

FLV vs MP4 — Flash Video vs the Modern Standard

FLV (Flash Video) was the dominant web video format from roughly 2005 to 2015 — YouTube, Vimeo, and virtually every video website used FLV. It required Adobe Flash Player to play, which was pre-installed on 98% of desktop browsers at peak adoption. Adobe officially ended Flash Player support on December 31, 2020. MP4 (H.264) replaced FLV as the web video standard, supported natively in all browsers via HTML5. FLV files are now legacy artifacts that need conversion.

FLVvsMP4

Quick Verdict

Use FLV when…

FLV has no compelling use case in 2025. Convert all FLV files to MP4. There is no reason to create new FLV files.

Use MP4 when…

Use MP4 for all video — web delivery, social media, mobile, and streaming. MP4 is the definitive video format for the post-Flash era.

FLV vs MP4: Feature Comparison

Feature	FLV	MP4
Requires Flash Player	Yes (Flash Player EOL Dec 2020)	No
Browser support	None (Flash blocked/removed)	Universal HTML5
Mobile support	Never supported on iOS	Universal
Video codec	Sorenson Spark or H.264 (F4V)	H.264 or H.265
File size efficiency	Poor (older codecs)	Excellent
YouTube historical use	Original format (pre-2010)	Current standard
Recommended for new use	No — use MP4	Yes

When FLV wins

✓Requires Flash Player: Yes (Flash Player EOL Dec 2020)
✓Browser support: None (Flash blocked/removed)
✓Mobile support: Never supported on iOS

When MP4 wins

✓Requires Flash Player: No
✓Browser support: Universal HTML5
✓Mobile support: Universal

Frequently asked questions

How do I convert FLV to MP4?

FFmpeg: `ffmpeg -i input.flv -c:v libx264 -crf 20 -c:a aac output.mp4`. HandBrake: open the FLV → select H.264 preset → set container to MP4 → Start. VLC: Media → Convert/Save → add FLV → choose H.264 + AAC MP4 profile → Start. Most online converters also handle FLV to MP4 conversion.

What is the difference between FLV and F4V?

FLV (Flash Video) uses older Sorenson Spark or On2 VP6 video codecs. F4V is Adobe's improved Flash container that holds H.264 video in an MPEG-4 container — essentially an MP4 renamed to .f4v. F4V files were used by Flash Player 9.0.115.0 and later for higher-quality streaming. Both FLV and F4V are obsolete; convert both to MP4.

Can VLC still play FLV files?

Yes — VLC Media Player includes FLV decoders and plays FLV files on Windows, macOS, Linux, Android, and iOS. VLC includes its own implementations of Sorenson Spark, VP6, and other FLV codecs. Even though Flash Player is dead, VLC can play any FLV file you have. For long-term preservation, convert to MP4.