Adobe Flash

Installation
There are several solutions to using Adobe Flash on Gentoo based systems. Some work in all browsers, while others only work in a select few. Following the Gentoo philosophy, choose the version that works best.

www-plugins/adobe-flash
The package is the official Linux implementation of Adobe Flash. Adobe has dropped support for any versions newer than 11.2 so this package may work for certain needs but is likely to be old, buggy, and contain many security vulnerabilities. Its use is not recommended.

To use this solution, run the following:

After emerging start or (restart if it was running) Firefox. An old, buggy, insecure version of Adobe Flash should now be available for use.

www-client/google-chrome-beta
Google Chrome includes the Pepper-based Flash plug-in which is much more up-to-date. Simply emerge to use flash in Chrome:

This will not setup flash for use for browsers outside of Chrome, but a Chrome plugin can be used to enabled Flash on Firefox. This is done with the freshflashplayer plugin (see the section below).

www-plugins/freshplayerplugin
The freshplayerplugin is a PPAPI-host NPAPI-plugin adapter for flashplayer in APAPI-based browsers. First

Next, open the Chrome browser at least one time. After Chrome opens install the package:

Then and start (or restart if it was already running) Firefox. A more recent version of Flash should now be available for use in Firefox.

Alternative
Alternative to flash using in case you just need to play video stream from youtube, vimeo, twitch, Internet TV-stream etc. is to install mpv player with lua USE-flag and libav/ffmpeg with openssl USE-flag. Lua gives the possibility for youtube-dl script to work in mpv and openssl gives libav/ffmpeg the possibility to open https:// streams from internet. Then you can install Open-with Firefox add-on and configure it in the following way:
 * Open about:openwith, select Add...
 * In the dialog select a video streaming capable player (e.g. /usr/bin/mpv).
 * (Optional step) Choose how to display the dialogs using the left panel of Open-with add-on.
 * Right click on links or visit pages containing videos. If the site is supported, the player will be open as expected.

The same procedure can be used to associate video downloaders such as youtube-dl.

= External links = Adobe Flash Player Archlinux article