Aegisub is a free, open-source software designed for creating and editing subtitles for videos. It supports various subtitle formats and provides tools for timing, styling, and translating text. Users can easily synchronize subtitles with audio and video, making it popular among fansubbers and video editors. The software features a user-friendly interface that allows for precise control over subtitle appearance, including font, color, and positioning. Additionally, Aegisub includes a built-in audio waveform viewer, which helps users accurately time their subtitles to match spoken dialogue.