Convert SubRip (.srt) to Advanced SubStation Alpha

SubRip (.srt) is the simplest widely-used caption format: a cue number, a HH:MM:SS,mmm --> HH:MM:SS,mmm timecode range, and a line or two of text. Advanced SubStation Alpha (.ass), the format Aegisub, many fansub groups, and advanced players like MPV and VLC use, is built for far more: a [Script Info] header, a [V4+ Styles] section defining fonts, colors, outlines, and screen position, and an [Events] section where each line of dialogue references one of those styles. It's a different structure entirely, not just a different timecode separator.

SubToolDesk's SRT to ASS converter parses your SRT cues locally in your browser, converts every timecode from SRT's millisecond format to ASS's centisecond H:MM:SS.cc format, and writes out a complete, valid .ass file: a working [Script Info] block, a single Default style sized and colored for general-purpose viewing, and one Dialogue: line per cue in the [Events] section.

How to convert SRT to ASS (step-by-step)

• Drag your .srt file onto the converter above, or click “Upload File” to browse for it.
• Confirm the auto-detected format badge reads SRT.
• Toggle Strip speaker labels or Strip formatting tags if your source has either.
• Press Download to save a valid .ass file, named to match your original file.

What the generated .ass file contains

The output is a complete, player-ready ASS file, not just a fragment. It includes a real [Script Info] block, a [V4+ Styles] section with one style named Default (white text, a thin outline and shadow for legibility over video, bottom-centered), and an [Events] section with a Dialogue: line for every cue, each referencing that Default style. You can open the result in Aegisub afterward to adjust fonts, colors, or position, the structural groundwork is already there.

Before and after

SRT input:
1
00:00:09,400 --> 00:00:12,900
Revenue was up eight percent.

ASS output:
[Script Info]
Title: SubToolDesk Export
ScriptType: v4.00+
...

[V4+ Styles]
Format: Name, Fontname, Fontsize, ...
Style: Default,Arial,20,&H00FFFFFF,...

[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:09.40,0:00:12.90,Default,,0,0,0,,Revenue was up eight percent.

Why timecodes look different in ASS

SRT times to the millisecond (00:00:09,400); ASS times to the centisecond, one-hundredth of a second, with a different separator and a non-zero-padded hour (0:00:09.40). The converter handles that rounding automatically, so a cue starting at 9.4 seconds in the source lands at the correct centisecond in the output, no manual recalculation needed.

Why people move from SRT to ASS

• Fansubbing and anime release groups, where ASS's styling and positioning overrides are the de facto standard for karaoke effects, signage translation, and per-character color coding.
• Editors working in Aegisub, which is built around the ASS format and expects it as a native project file rather than a plain SRT import.
• Players and pipelines that render styled overrides, like MPV or certain streaming encoders, where SRT's plain text can't carry positioning or font instructions at all.
• Starting a styled subtitle project from an existing plain transcript, using this converter to get a structurally valid ASS file in place before adding styles by hand.

Privacy by architecture, not by policy

Parsing the SRT and writing the ASS file both happen in JavaScript running in your browser tab. There is no upload endpoint this feature could hit, which matters as much for a pre-release fansub script as it does for a confidential corporate video.

What this tool intentionally doesn't do

It writes one Default style and doesn't attempt to guess at karaoke timing, per-character colors, or positioning overrides, those are a manual (or Aegisub-assisted) step once you have a valid base file. It also won't parse an existing .ass file's own styling back out if you convert in the other direction; this tool is built for getting plain caption text into valid ASS structure, not round-tripping an already-styled one.