SMI to VTT
Or paste subtitle text
What this conversion changes
2 things are dropped or need a decision
- Positioning
on-screen positioning (every cue returns to the default position)
- 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 VTT. Drop a file in — or paste the text — and you get the VTT 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: positioning and format-specific content have nowhere to go in VTT. 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 VTT
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
WEBVTT
00:00:01.000 --> 00:00:03.000
Hello there.
00:00:03.500 --> 00:00:06.000
How are you?
Fine, thanks.
Dropped in this output: positioning 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
WEBVTT
00:00:02.500 --> 00:00:09.000
Line one
Line two
00:00:09.000 --> 00:00:12.000
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
What happens to the on-screen position from SMI to VTT?
VTT cannot say where a subtitle is drawn, so the paragraph attributes and the CSS they point at are dropped on the way out of SMI, and every cue goes back to the default position the player chooses — the bottom of the frame, centred, for most of them.
What happens to SAMI's `<STYLE>` block, `<TITLE>` and `Class=` attributes in VTT?
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. VTT 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 VTT?
Like VTT: an optional identifier line above each cue, which no player ever displays. Every SMI cue becomes one VTT cue, in the same order, with the same text.
Are the SMI timings exact in the VTT file?
Yes, to the millisecond — which is as fine as either format goes. SMI writes a moment as `Start=4126` and VTT writes the same moment as `00:00:04.126`; nothing is rounded or shifted between the two, and a cue that was on screen for 2.9 seconds still is.
How does a two-line SMI cue come out in VTT?
As two lines, one under the other. The pairing survives — the two SMI lines still belong to one subtitle in the VTT output, and a player shows them together.
Do SMI cues keep their order in the VTT 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 VTT 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 VTT back to SMI?
Yes, and it has its own list: converting VTT to SMI drops format-specific content. That list is different from the one above because the two formats keep different things.
Does the VTT 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 VTT.