Getting started:

Step 1: Install

Grab CardSpotter from the Chrome Web Store. here

Step 2: Watch the demo

Just to get a rough idea of how it works - watch the short demo. here

Step 3: Pick one of these example

Step 4: Start CardSpotter

Toolbar Icon After the video has started you can enable CardSpotter. You do that by clicking the toolbar icon.
Tooltips should now automatically appear as cards are played.
If they do not - click the card you want a tooltip for.
If that still doesn't work - please continue to 4.1.

Step 4.1: Troubleshooting

If the video starts to flicker, or no card shows up at all, that could indicate GFX issues. Try to disable Chrome hardware acceleration or update your drivers.

The example video is forced to play in HTML5 mode, CardSpotter only supports HTML5 players, if you have issues with this when trying other videos please consult the documentation on how to change the video player settings.

Step 5: Find the controls

Overlay menu When CardSpotter is enabled a small magnifying glass and a dropdown menu is shown in the lower right of the video.

If you do not start the video before you enable CardSpotter there is no video information available and CardSpotter will most likely complain that the video resolution is not optimal.

If you want to temporarily disable CardSpotter to perhaps change some video settings - click the magnifying glass with the - sign to minimize it. Click it again to bring the menu and CardSpotter back.
CardSpotter works by capturing mouse clicks using an invisible overlay. The relative size of this can be configured under the extension options.
The extension options can be accessed by right-clicking the CardSpotter toolbar icon and selecting "Options".

Step 6: Enjoy

Either you check out some more examples that are known to work relatively well in the examples section of the DOCUMENTATION (both twitch/youtube).
Or play around with it on one of your favorite streams. But please, do let me know how it goes. Either by rating the extension if everything is awesome, or if something is broken by emailing me at jonas@cardspotter.com so that I have a chance to fix it.