What is a SUB file?
A .SUB file is a data file that contains subtitle information for videos, or subchannel data for optical disks. Because the .SUB extension is used by many different programs, its internal format can vary significantly.
The most common use is the VobSub subtitle format. These .SUB files contain bitmap images of subtitles extracted from a DVD. They are usually paired with an .IDX file that controls the timing. Another common subtitle format is the MicroDVD Subtitle File originally developed by Tiamat Software.
Beyond subtitles, a .SUB file can be a CloneCD Subchannel Data File created by SlySoft. It can also be a Sub-Gigahertz signal capture file for a Flipper Zero device, a game UI sprite file for the Metin2 game client, a SubTerra Level File from Crystal Shard, or an LTspice subcircuit simulation model from Analog Devices.
How to open and inspect SUB files?
You need different software depending on the specific file format. For video subtitles, VLC media player and MPC-HC can easily load .SUB files alongside video files. If you have a CloneCD image, you need optical disc authoring software like VirtualCloneDrive or Daemon Tools to mount it.
Because .SUB has multiple possible meanings, it is difficult to know which software to use. viewer.online/sub can analyze .SUB files to identify the exact format and creator software, inspect the file structure, extract readable text, and check whether an online preview is available.
File conversion
Converting a .SUB file depends on its actual content. If your file contains text-based subtitles, you can convert it to more standard formats like .SRT or .VTT. We recommend using convert.guru to convert your .SUB files to sensible target formats. If the file is a VobSub bitmap, conversion requires Optical Character Recognition (OCR) tools like Subtitle Edit to read the text from the images.
Summary
A .SUB file can store video subtitles, disk image subchannel data, or hardware signal captures. Identifying the correct format is the first step to opening it. This is why viewer.online/sub is useful for identifying, inspecting, and understanding .SUB files without installing software or dealing with compatibility problems.