Convert FLV to WebM Online
Convert legacy Flash FLV videos to modern WebM. Free, in your browser, no file uploads.
.flv · up to 100 MB
What you can do
Rescue Flash-era videos for the modern web
No Flash Player
WebM plays natively in Chrome, Firefox, and Edge. The post-Flash world without installations.
100% private
Your FLV files never leave your device. Re-encoding happens locally in WebAssembly.
YouTube archive
Modernize YouTube videos downloaded before 2012 in FLV to a format playable today.
Sorenson, VP6 and H.264
Compatible with all three video codecs that FLV can contain — any FLV file works.
How it works
Three steps, no hassle
Upload your FLV file
Drag or select the .flv — videos downloaded from YouTube before 2012, old Flash Video files, or Adobe Flash exports. No signup.
VP8 re-encoding in the browser
Sorenson Spark, VP6, or H.264 video encapsulated in FLV is decoded and re-encoded to VP8 directly on your device via WebAssembly.
Download your WebM
A .webm file ready to embed in HTML5, play without Flash Player, or publish on modern video platforms.
FAQ
Got questions?
FLV (Flash Video) is a video format created by Macromedia in 2002 (Macromedia was acquired by Adobe in 2005 for $3.4 billion). FLV was the dominant web format between 2005 and 2012: YouTube used it from its founding in 2005 until it progressively adopted HTML5 from 2010. The problem is that FLV requires Flash Player to play in browsers, and Adobe announced Flash Player's end of life on December 31, 2020. All modern browsers actively blocked Flash from 2017 and removed it completely in 2021. FLV files can no longer be played in any browser without third-party tools.
No, FLV files can contain three different video codecs: (1) Sorenson Spark (also called FLV1), based on H.263, introduced in Flash Player 6 (2002) — the first YouTube videos used this codec; (2) On2 VP6 (FLV4), introduced in Flash Player 8 (2005), offers better quality than Sorenson Spark but still inferior to H.264; (3) H.264 (also called AVC) in an FLV container, introduced in Flash Player 9 Update 3 (2007) — high-quality YouTube videos from 2007 onward used H.264 in FLV. For audio, FLV can use MP3, AAC, or Nellymoser. The converter handles all three FLV video types.
In 2005, when YouTube was founded, MP4 with H.264 was not technically viable for web streaming because H.264 was not available in browsers without plugins. Flash Player was the de facto standard for web video playback, installed on over 95% of desktop browsers. FLV with Sorenson Spark offered acceptable quality at low bitrates (crucial for 1-2 Mbps broadband connections of the time) and could play with the ubiquitous Flash Player. YouTube migrated to H.264 within FLV in 2007, and began offering HTML5 with MP4/H.264 in 2010, completing the FLV to MP4 transition around 2012.
Yes, if the FLV file is not DRM-encrypted. YouTube videos downloaded via tools like youtube-dl before 2012 are generally DRM-free FLV and can be converted to WebM without restrictions. Metadata embedded in the FLV (title, tags) is not always transferred to the resulting WebM, but the video and audio content converts completely.
It depends on the original codec and conversion settings. If the FLV uses Sorenson Spark or VP6, conversion to VP8 can even visually improve the result at similar bitrates because VP8 is a more efficient codec. If the FLV uses H.264, transcoding to VP8 involves a re-encoding generation with some quality loss; the degree depends on the configured output bitrate. For maximum fidelity from H.264-in-FLV, converting to WebM with VP9 or directly to MP4 would be recommended, although for most uses the VP8 result is visually acceptable.
WebM has specific advantages over MP4 for certain web uses: (1) WebM is completely royalty-free under Apache 2.0 and BSD licenses, while H.264 in MP4 requires patent pool licenses managed by MPEG LA (though free internet distribution has been allowed without royalty payments since 2010); (2) WebM with Opus (the successor to Vorbis) offers better audio quality at low bitrates than AAC; (3) some web publishing platforms and open-source CMS systems have better WebM support. For most uses, MP4 with H.264 is equally valid, but WebM is the native open-source option for HTML5.
Convert FLV to WebM: rescue Flash videos for the modern web
FLV (Flash Video) is one of the most historically important video formats on the internet, even though it is completely unusable in modern browsers today. It was created by Macromedia in 2002 for its Flash MX product, and when Adobe acquired Macromedia in 2005 for $3.4 billion, it inherited both Flash Player and the FLV format. The historical importance of FLV is enormous: it was the format that made mass web video possible. YouTube, founded in February 2005 by Chad Hurley, Steve Chen, and Jawed Karim (former PayPal employees), chose FLV with the Sorenson Spark codec for its first videos precisely because Flash Player was installed on over 95% of desktop browsers. Dailymotion (2005), Metacafe (2003), Google Video (2005), and virtually all video platforms of the era adopted FLV. The first video uploaded to YouTube, 'Me at the zoo' by Jawed Karim on April 23, 2005, was an FLV file with Sorenson Spark. The format evolved: in 2007 YouTube began using H.264 encapsulated in FLV for its high-quality videos, and in 2010 the transition to HTML5 with MP4 began.
The decline of FLV is directly linked to the decline of Flash Player. Steve Jobs published his famous 'Thoughts on Flash' letter on April 29, 2010, explaining why the iPhone would never support Flash, and that same year Google announced WebM as an open alternative. HTML5 with the <video> tag was progressively adopted by all browsers, and Flash Player began losing relevance. The decisive moment came when Adobe announced on July 28, 2017 that Flash Player would be discontinued on December 31, 2020. Browsers actively blocked Flash from 2017, and on January 12, 2021, Adobe published an update that blocks the execution of any Flash content. The result is that a huge corpus of historical, educational, and archival videos in FLV format are no longer directly playable in any browser and need to be converted to modern formats to be preserved and published.
The technical conversion of FLV to WebM involves several scenarios depending on the encapsulated video codec. Sorenson Spark (FLV1), based on modified H.263, is the oldest and lowest-quality codec — conversion to VP8 at the same bitrate will produce a visually superior WebM because VP8 uses more efficient compression. On2 VP6 (FLV4), introduced in Flash Player 8 in 2005, is also less efficient than VP8, so conversion can maintain or improve visual quality. H.264 encapsulated in FLV is the most complex case: H.264 and VP8 have similar compression efficiencies, and transcoding involves an additional loss generation. Convertir.ai processes all these cases via WebAssembly in the browser, keeping file data completely on the user's device. This is especially relevant for archival and educational files that may represent valuable creative or historical work that should not be processed on external servers.