You would think this should be built into html5, Oh well. I guess I can live without it because my project is only going to be run locally :/

Thenior is (semi-) right. Common "search-nails" features are based upon a server-side processes. Its results are usually pumped into the players via async requests providing URLs to pre-processed thumbnails, setting them in relation to a given time index.

For sure it´s possible to achieve similar effects strictly on client side by creating thumbs via <canvas> and featuring a "preloading" <video>-element. Buts this is a hack and not covered by Projekktor´s "least common dominator"-principle.

To make long words short: Not yet.

- sascha