What happens to malformed STL lines?

Lines without recognizable start time, end time, and text are skipped. Empty cues are not emitted.

Can I convert multiple STL files?

Drop several valid files on this page and they open together in the workspace Batch tool with TTML preselected. The batch workflow supports up to 200 files.

What is the maximum file size?

Each subtitle file can be up to 50 MB.

What language does the TTML document declare?

The generated document uses xml:lang="en". It does not infer or preserve a source language declaration.

STL to TTML Subtitle Converter

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STL

// Spruce Subtitle File
// Format: Start Time, End Time, Subtitle Text
 
00:00:01:00 , 00:00:04:00 , Hello, world!
00:00:04:15 , 00:00:08:00 , This is a subtitle file.
00:00:08:15 , 00:00:12:00 , Converted locally!

TTML

<?xml version="1.0" encoding="UTF-8"?>
<tt xml:lang="en" xmlns="http://www.w3.org/ns/ttml">
  <body>
    <div>
      <p begin="1.000s" end="4.000s">Hello, world!</p>
      <p begin="4.500s" end="8.000s">This is a subtitle file.</p>
      <p begin="8.500s" end="12.000s">Converted locally!</p>
    </div>
  </body>
</tt>

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Supports .stl files up to 50 MB

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How It Works

Upload STL File

Drag & drop or select your .stl file

Convert Instantly

We process it locally in your browser

Download TTML

Get your .ttml file immediately

More Conversions You Might Need

STL TTMLSTL SRT STL VTT STL ASS STL LRC STL TXT STL SCC STL SMI

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SRT TTML VTT TTML ASS TTML LRC TTML SBV TTML SSA TTML SCC TTML SMI TTML

Why Choose AllSubConverter?

Your Privacy Matters

Everything runs in your browser. Your files are never uploaded.

Lightning Fast

Optimized processing engine converts files in seconds.

Free & Local

Each file can be up to 50 MB. Batches can contain up to 200 files or 1 GB total.

Works Everywhere

Works on Windows, Mac, Linux, iOS, Android - any modern browser.

Free Online STL to TTML Converter

This converter reads text-based Spruce STL entries and writes a basic TTML document. Cue timing becomes second-based begin and end attributes, line breaks become elements, and XML special characters are escaped. The conversion runs locally in your browser, so the subtitle file is not uploaded.

Input Format

STL

STL here refers to text-based Spruce Subtitle cue lines containing a start time, an end time, and subtitle text. Vertical bars are used as line separators, and bracketed inline tags may appear in the source text. Binary EBU STL is a different format and is not parsed by this converter.

Output Format

TTML

TTML (Timed Text Markup Language) is an XML format for timed text. This converter emits a basic UTF-8 document with the default TTML namespace, xml:lang="en", a body and div, and elements carrying begin and end times. It does not add optional delivery profiles or styling metadata.

Features

Reads text-based Spruce STL cue lines

Writes a basic UTF-8 TTML document

Converts cue timing to second-based begin and end attributes

Converts line breaks to elements

Escapes XML special characters

Processes files locally without uploading them

Why Convert?

TTML is useful when an XML timed-text workflow expects begin and end attributes.

TTML represents line breaks explicitly with elements.

TTML is a structured interchange format for timed text.

Converting STL text and timing can make older cues easier to inspect in XML tools.

Format Differences

Spruce STL uses text cue lines; TTML uses an XML document.

STL commonly separates lines with vertical bars; TTML uses elements.

STL timing is parsed from the source time fields; this output uses TTML second-based timing.

The output is basic TTML and does not include optional styling or delivery-profile metadata.

Common Use Cases

XML Subtitle Preparation

Convert supported STL cues into a basic TTML document for tools that accept timed-text XML.

Line-Break Conversion

Turn vertical-bar STL separators into TTML line-break elements.

Timing Inspection

Review explicit start and end times in a structured TTML document.

Related Formats

SRT (SubRip)

Convert STL to SRT when you need a widely supported plain-text subtitle file.

VTT (WebVTT)

Convert STL to VTT for a plain cue format commonly used with web video.

TXT (Plain Text)

Convert STL to TXT when timing is not needed and only the text matters.

Frequently Asked Questions

Does this converter create Netflix or IMSC delivery files?

No. It creates a basic TTML document with cue timing and text. Delivery profiles and their required metadata are not generated.

Is special text escaped?

Yes. Ampersands, less-than signs, and greater-than signs are escaped for XML.

Does it preserve STL styling?

No. Common bracketed inline tags are removed, and the TTML output does not add a styling model for them.

How are line breaks represented?

Source line breaks are written as elements inside each TTML element.

Is the STL to TTML converter free?

Yes. There is no registration or watermark, and conversion happens in your browser.

Is my data sent to a server?

No. Processing stays in your browser and the subtitle file is not uploaded.

Ready to convert your subtitles?

Drop your STL file here and convert to TTML instantly.

Related Resources

What is STL?What is TTML?TTML vs STL ASS vs STL ASS vs TTML LRC vs STL