.ASS File Format

Introduction

Advanced SubStation Alpha (.ass) is version 4.00+ of the SubStation Alpha script format. It added layers, an alpha channel in colours, rotation and scaling in styles, and many override tags for movement, fades and vector drawing. It is the format most fan subtitling uses, and Aegisub, libass and VSFilter are its main implementations.

The written specification covers much of it, but in practice the format is defined by what VSFilter and libass do.

Structure

The file is text in INI-like sections, each beginning with a name in brackets, and ScriptType: v4.00+ in its [Script Info] section. The full reference is in the pages below.

• Script info – the header and its keys
• Styles – the named styles of [V4+ Styles] and their 23 fields
• Events – dialogue, comments and effects in [Events]
• Override tags – every tag inside text in braces
• Fonts and graphics – embedded files and how they are encoded

[Script Info]
ScriptType: v4.00+
PlayResX: 1920
PlayResY: 1080

[V4+ Styles]
Format: Name, Fontname, Fontsize, PrimaryColour, Bold, Italic, Alignment, MarginV
Style: Default,Arial,64,&H00FFFFFF,0,0,2,40

[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:01.00,0:00:03.50,Default,,0,0,0,,Where are we going?
Dialogue: 0,0:00:04.00,0:00:06.25,Default,,0,0,0,,{\i1}Somewhere we have never been.{\i0}

Variants

• SubStation Alpha v4.00 – the older .ssa scripts, with [V4 Styles] and legacy alignment codes
• Advanced SubStation Alpha v4.00+ – .ass scripts, with layers, alpha and numeric-keypad alignment

Links