SMI to ASS
Or paste subtitle text
What this conversion changes
2 things are dropped or need a decision
- Precision
timing precision — the output's clock is coarser, so every timestamp is rounded to the nearest 10 ms
- Format-specific content
content the source format keeps outside its cues (non-cue blocks, header text, per-cue settings, commented-out events) — the target format has no place for it
This list comes from the capability matrix for these two formats, not from the particular file you loaded. A specific file may lose more if it uses features the format allows but the matrix does not model.
This page converts SMI to ASS. Drop a file in — or paste the text — and you get the ASS version back. The conversion runs entirely in your browser, so nothing is uploaded and no account is needed.
These two formats do not store the same things, and the difference is not cosmetic: precision and format-specific content have nowhere to go in ASS. The list above comes from what the two formats can each express rather than from your file, so it is the same answer before you load anything.
One file is fine, and so is a whole season: the queue works through them in order and the results come down together as a single ZIP.
Examples
A typical SMI file, converted to ASS
Input
<SAMI>
<HEAD>
<STYLE TYPE="text/css">
<!--
P { text-align: center; font-family: Arial; }
.ENCC { Name: English; lang: en-US; }
-->
</STYLE>
</HEAD>
<BODY>
<SYNC Start=1000>
<P Class=ENCC>Hello there.
<SYNC Start=3000>
<P Class=ENCC>
<SYNC Start=3500>
<P Class=ENCC>How are you?<br>Fine, thanks.
<SYNC Start=6000>
<P Class=ENCC>
</BODY>
</SAMI>
Output
[Script Info]
ScriptType: v4.00+
[V4+ Styles]
Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding
Style: Default,Arial,20,&H00FFFFFF,&H000000FF,&H00000000,&H00000000,0,0,0,0,100,100,0,0,1,2,2,2,10,10,10,1
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:01.00,0:00:03.00,Default,,0,0,0,,Hello there.
Dialogue: 0,0:00:03.50,0:00:06.00,Default,,0,0,0,,How are you?\NFine, thanks.
Dropped in this output: precision and format-specific content. Everything else matches line for line.
The same conversion on an awkward input
Input
<SAMI>
<HEAD>
<TITLE>Episode 1</TITLE>
<STYLE TYPE="text/css">
<!--
.ENCC { Name: English; }
-->
</STYLE>
</HEAD>
<BODY>
<sync start="00:00:02,500">
<P Class=ENCC>Line one<br>Line two
<sync start=9000>
<P Class=ENCC>Tom & Jerry
<SYNC Start=12000>
<P Class=ENCC>
</BODY>
</SAMI>
Output
[Script Info]
ScriptType: v4.00+
[V4+ Styles]
Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding
Style: Default,Arial,20,&H00FFFFFF,&H000000FF,&H00000000,&H00000000,0,0,0,0,100,100,0,0,1,2,2,2,10,10,10,1
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:02.50,0:00:09.00,Default,,0,0,0,,Line one\NLine two
Dialogue: 0,0:00:09.00,0:00:12.00,Default,,0,0,0,,Tom & Jerry
This is the kind of damage real files have — mixed line endings, stray whitespace, fields left empty. Compare it with the tidy example above to see what the parser forgives.
Frequently asked questions
Why have the timestamps moved from SMI to ASS?
ASS stores time as `0:00:04.13` where SMI stores it as `Start=4126` — a hundredth of a second against a thousandth — so every timecode is rounded to the nearest 10 ms: 00:00:04,126 comes out as 4.13 seconds. Nothing is stretched or reordered and no cue moves by more than 5 ms, but if you are lining these subtitles up against another file, that is the one place this conversion stops being exact.
What happens to SAMI's `<STYLE>` block, `<TITLE>` and `Class=` attributes in ASS?
They are dropped. SAMI says what its subtitles look like outside the text of the cue: a `<STYLE>` block of CSS for the paragraphs, a `<TITLE>`, and the channel marker each paragraph carries — `Class=ENCC`, which points at one of those rules. ASS stores cues rather than a document, so there is nowhere for any of that to go. Emphasis written inside a cue's own text is unaffected — that belongs to the line — and the cues come through with their text and timings whole.
What does the output look like when SMI becomes ASS?
Like ASS: no cue numbers: every subtitle is a `Dialogue:` line in the `[Events]` section, with a layer field where SRT keeps the number. Every SMI cue becomes one ASS cue, in the same order, with the same text.
How does a two-line SMI cue come out in ASS?
As two lines with `\N` between them, which is how ASS writes a hard line break. The pairing survives — the two SMI lines still belong to one subtitle in the ASS output, and a player shows them together.
Do SMI cues keep their order in the ASS output?
Yes, and they are sorted by start time on the way — earliest first, which is how every format here expects them and how players read them. If your SMI file listed its cues out of sequence, the ASS output puts them back in order; that is a change to the file's structure rather than its content, and it is deliberate.
Can I convert the ASS back to SMI?
Yes, and it has its own list: converting ASS to SMI drops styling, karaoke and format-specific content. That list is different from the one above because the two formats keep different things.
Does the ASS output keep the SMI file's encoding?
No — the output is UTF-8, with Unix line endings and no byte-order mark, whatever the SMI file used. A file that arrives in UTF-16, or in a Windows single-byte encoding, is decoded on the way in (the result panel says so when that happens); what comes out is always the same UTF-8 ASS.