Anyone who works on video projects (or who wants to beef up the GIFs/memes folder on their phone) occasionally needs to download videos from YouTube, TikTok, Instagram, and similar sites. The problem is that such sites usually don't offer a download button, leaving you to turn to a third-party application, which introduces another problem: those third-party tools are frequently riddled with ads or generally scammy looking.
Not Cobalt.tools. This service, built by a single person, is completely open source and features no ads, trackers, or analytics. It also couldn't be simpler to use: just copy the URL for the media you want to download and paste it on the site. Your download will start after you hit "Enter".
Most people don't need to know anything else in order to download videos but there are a few features you can dig into if you really want: You can pick the video's resolution, turn off that annoying TikTok watermark, and download actual (ancient, inefficient) .gif files from Twitter instead of a video file. You can also customize the eventual file name, using the name of the video instead of the URL if you prefer. (Keep in mind that downloading and using videos from social media may violate the site's terms of service. Depending on how the video is used, it may also be considered copyright infringement.)
According to the project page on Github the site supports downloading videos and audio files from Bilibili, Instagram, OK Video, Pinterest, Reddit, Rutube, Soundcloud, Streamable, Tiktok, Tumblr, Twitch (clips), the website formally known as Twitter, Vimeo, Vine, VK, and YouTube. That should cover just about everything.