There are tons of tools that let you download, convert or merge videos online, but very few that allow you to do all of these from a single platform. That is why I like Movavi.
Movavi has three main features:
Using Movavi you can download videos from sites like YouTube and Google Video by simply specifying the URL. You can enter the URLs of upto 5 videos and start downloading them simultaneously.
Movavi also lets you convert videos to and from various formats including flv, avi, mpeg, mov, mp4 and others. You can specify a URL of an online video or upload a video from your local drive to convert. You can also convert a video to mp3 in order to extract the audio.
Movavi also lets you adjust different presets so you can customize your output.
You can also merge all these videos into a single movie. No need to install any video editing software, simply do it online with Movavi.