How are line breaks represented?

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

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

Convert Spruce STL cue timing and text into a basic Timed Text Markup Language document.

Drag & drop your STL file here

or click to browse

Supports .stl files up to 50 MB

Core Engine Architecture

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.

Payload & Syntax Inspector

STL to TTML Code Syntax & Structure Inspection

Side-by-side code inspection illustrating header definitions, timestamp syntax, and cue payload formatting

Millisecond Sync

input.stl

STL SOURCE

// 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!

output.ttml

TTML RESULT

<?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>

Specification Sheet

STL vs TTML Technical Specifications

Standard Compliant

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.

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.

Conversion Troubleshooting & Gotchas

Practical solutions for player compatibility, character encoding, and timing synchronization

4 Common Gotchas

GOTCHA #1

Subtitle timing drifts or appears out of sync on media players

Video files frequently differ in framerate (e.g., 23.976 fps vs 25 fps). If the timing drifts steadily, use our Subtitle Sync tool to adjust the global offset or framerate stretch.

GOTCHA #2

Characters appear as garbled symbols or question marks (Mojibake)

Legacy files saved in Windows-1252, Shift-JIS, or GBK may render incorrectly. Our exporter standardizes output to clean UTF-8. Use our Subtitle Encoding Converter if the source file is corrupted.

GOTCHA #3

Overlapping captions when multiple speakers talk simultaneously

Different formats handle overlapping dialogue differently. If your target player cannot render stacked cues cleanly, open the file in our Subtitle Editor to adjust individual cue timings.

GOTCHA #4

Video editing software (Premiere, DaVinci, Final Cut) rejects the file

Professional NLE software enforces strict syntax rules. Our converter eliminates malformed line breaks and non-standard tags, producing clean, standardized files.

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.

Scenarios

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.

Format Ecosystem

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.

How It Works

1
Select or drop a text-based STL file.
2
Start time, end time, and text are read from each valid cue line.
3
Vertical bars become line breaks and common bracketed inline tags are removed.
4
Each cue is written as a TTML element with begin and end times.
5
Download the generated .ttml file.

moreTools.fromFormat

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

moreTools.toFormat

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

More Subtitle Tools

Subtitle Format Cleaner

Remove formatting, tags and noise

Subtitle Editor

Edit subtitle content and timings

Subtitle Sync & Timing Calibration

Adjust timing with millisecond precision

Subtitle Merger

Combine multiple subtitle files

AI Subtitle Translator

Translate to 19 built-in target languages

Frequently Asked Questions

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

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

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

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

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

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.

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Related Resources

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