GlossaryFLV

FLV

FLV (Flash Video) is a video container format created for Adobe Flash Player to deliver video over the internet. FLV files were the standard for web video in the 2000s, including on early YouTube. Since Flash reached end of life in 2020, browsers no longer play FLV, though the format lives on inside RTMP live streaming.

Why it matters

Browsers no longer play FLV, so old FLV archives must be converted before they can be watched again. FLV also still matters for live video, because the RTMP protocol many encoders use carries FLV-style data. Teams building live streaming need to understand it even if they never see an .flv file.

How it works

  1. FLV stores video and audio as a series of tagged packets with timestamps.
  2. In live streaming, an encoder wraps these packets in RTMP and sends them to a server.
  3. The server unpacks the stream and transmuxes or transcodes it into HLS or another web format.
  4. For archives, converters read old FLV files and re-encode them into MP4.

Can you still play FLV files?

Browsers can no longer play FLV files, because Adobe ended Flash Player support at the end of 2020. Desktop players such as VLC can still open them. For web or app playback, FLV files need converting to MP4 or an adaptive streaming format such as HLS.

What is the relationship between FLV and RTMP?

RTMP was built to carry Flash video, so its packets use the same audio and video tag structure as FLV. That is why many encoders and servers still describe RTMP output as FLV. When a server receives an RTMP stream, it typically repackages it into HLS for viewers. Going live on FastPix takes that repackaging off your hands: point the encoder at FastPix over RTMPS or SRT, the encrypted options it accepts in place of plain RTMP, and viewers receive the stream as LL-HLS.

Where it's used

Live sports streamers and creator apps meet FLV inside RTMP, the protocol many encoders use to send live video. Video platforms also migrate old FLV archives into modern formats.

By the numbers

  • Adobe ended support for Flash Player on December 31, 2020, and blocked Flash content from running beginning January 12, 2021. (Adobe Flash Player End of Life)
  • Flash Video was first released on September 10, 2003, when Flash Player 7 added direct support for the format. (Flash Video (Wikipedia))

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