What happens to malformed STL lines?

Lines that do not contain recognizable start time, end time, and text are skipped. Empty cues are not emitted.

Can I batch convert STL files?

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

What is the maximum file size?

Each subtitle file can be up to 50 MB.

Can I use the result as an HTML5 track?

The output is a basic WebVTT file, but player support can depend on the browser and how the track is served.

STL to VTT Subtitle Converter

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100% local processing in your browser. No upload. No waiting.

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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!

VTT

WEBVTT
 
00:00:01.000 --> 00:00:04.000
Hello, world!
 
00:00:04.500 --> 00:00:08.000
This is a subtitle file.
 
00:00:08.500 --> 00:00:12.000
Converted locally!

Drag & drop your STL file here

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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 VTT

Get your .vtt file immediately

More Conversions You Might Need

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

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 VTT Converter

This converter reads text-based Spruce STL entries and writes a basic WebVTT file. The output starts with a WEBVTT header, each cue receives dot-separated start and end timestamps, and cue line breaks remain physical text lines. Parsing and conversion stay 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 separate display lines and bracketed inline tags may appear in the source. Binary EBU STL is not supported by this converter.

Output Format

VTT

VTT (WebVTT) is a text subtitle format for web video. This converter emits the WEBVTT header followed by plain cues with HH:MM:SS.mmm --> HH:MM:SS.mmm timing and text. It does not add optional cue identifiers, cue settings, styling, or metadata blocks.

Features

Reads text-based Spruce STL cue lines

Adds the WEBVTT header required by the format

Converts supported STL times to VTT millisecond timestamps

Turns vertical-bar separators into normal VTT line breaks

Removes common bracketed inline tags

Processes files locally in your browser

Why Convert?

Web video players commonly expect VTT rather than an authoring-oriented STL file.

VTT uses millisecond timestamps and a simple web-oriented cue structure.

VTT keeps explicit start and end times for every cue.

Converting STL text and timing can make it easier to test in a browser video player.

Format Differences

Spruce STL uses comma-separated text cue lines; VTT uses WEBVTT cue blocks.

STL commonly separates lines with vertical bars; VTT uses physical text lines.

VTT timestamps use a period before milliseconds.

The generated VTT does not include optional cue settings or styling.

Common Use Cases

Web Video Testing

Convert supported STL cues into basic VTT for testing in an HTML5 video workflow.

Line-Break Conversion

Turn vertical-bar STL separators into ordinary VTT text lines.

Subtitle Reuse

Move text and timing from supported STL files into a web-oriented subtitle format.

Related Formats

SRT (SubRip)

Convert STL to SRT for a widely supported plain-text subtitle format.

TTML (Timed Text Markup Language)

Convert STL to TTML when your workflow expects timed-text XML.

TXT (Plain Text)

Convert STL to TXT when you only need the dialogue text.

Frequently Asked Questions

Does this converter support EBU STL files?

No. It reads text-based Spruce STL cue lines, not binary EBU STL files.

How are line breaks handled?

STL vertical bars are converted into normal line breaks inside each VTT cue.

Does it preserve STL styling?

No. Common bracketed inline tags are removed and no source styling is mapped.

Does the output include VTT cue settings?

No. The output contains basic cues with timing and text. Position, alignment, size, and styling settings are not generated.

Is the STL to VTT converter free?

Yes. There is no registration or watermark, and processing 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 VTT instantly.

Related Resources

What is STL?What is VTT?VTT vs STL ASS vs STL LRC vs STL SBV vs STL