An AVS file is typically a small plain-text AviSynth instruction set defining how to load and process video—resizing, cropping, trimming, deinterlacing, denoising, sharpening, frame-rate changes, or adding subtitles—which you open either in a text editor or in VirtualDub2/AvsPmod to run and preview before encoding via ffmpeg or similar tools; readable commands like LoadPlugin, plus tiny filesize, identify it as AviSynth, while preview issues usually come from missing filters, nonexistent file paths, or version mismatches, though in some contexts "AVS" instead refers to other programs’ config/project files that don’t behave like AviSynth scripts.

An AVS file may function as an AVS4YOU project file, meaning it stores the structure of your edit—timeline layout, imported clips, trims, splits, transitions, titles, effects, audio changes, and export settings—so it’s small because it holds references rather than actual video, which is why it won’t play in VLC or look meaningful in Notepad and must be opened inside AVS Video Editor, where missing clips appear if source files were moved or removed, and sharing the project requires copying both the AVS file and all referenced media in the same folder structure.

When I say an AVS file is usually a script/project file, I mean it stores no actual footage, functioning either as an AviSynth text script that instructs the software to load video and apply operations like trimming, cropping, resizing, deinterlacing, denoising, sharpening, frame-rate changes, and subtitles, or as an editor project saving timeline edits and references to external media, which is why AVS files are small, non-playable in standard players, and must be opened in a text editor or the program that created them so the instructions can be executed.

If you are you looking for more info about AVS file windows take a look at the page. What’s inside an AVS depends on its origin, but in the typical AviSynth sense it contains readable, code-like lines that outline a full video-processing chain: it starts by loading the source with a function pointing to an AVI/MP4/MKV, may load extra plugins, then applies steps like trimming, cropping, resizing, deinterlacing, denoising, sharpening, frame-rate handling, color tweaks, or subtitles, with each line either loading, transforming, or preparing the video for output, so errors such as "no function named …" or "couldn’t open file" usually indicate missing plugins or invalid paths.