Free tool
STL to SRT converter
Drop a broadcast subtitle file here to convert STL to SRT: the EBU STL’s binary blocks are decoded in your browser, accented letters and italics included, and every subtitle comes out with its times, counted from the programme start so they match the video file.
- Free
- No sign-up
- Nothing is uploaded
Drop an .stl file here
EBU STL from broadcast, or Spruce STL from DVD Studio Pro.
Nothing is uploaded: your browser reads the file.
Subtitling programmes from your own recordings? NoteOwl transcribes them on your Mac, unlimited, and saves SRT files with each speaker’s name.
How it works
How do you convert an STL file to SRT?
Open the .stl here. The converter reads the file’s header for its frame rate, character table and programme start, then each subtitle block for its text and times, and writes the SRT. Untick the programme start if your video is timed from it.
- 1
Add the STL
Drop the .stl or choose it. The line under the box names the frame rate, alphabet and title it found.
- 2
Check the start time
Times count from the programme start the file declares, such as 10:00:00:00, so the first minute is 0:00.
- 3
Download
SRT for most players and editors, VTT for a web player, or text to read the dialogue.
What does an EBU STL file look like inside?
Unlike SRT, it isn’t text. Here are the first bytes of a small EBU STL file, its header block and two subtitle blocks, and the SRT this page writes from it. The second subtitle starts 4.4 seconds after the programme start, 10:00:04:10.
GSI block (1,024 bytes), first 32: 0000 38 35 30 53 54 4c 32 35 2e 30 31 30 30 30 30 39 850STL25.0100009 0010 62 75 6c 6c 65 74 69 6e 20 20 20 20 20 20 20 20 bulletin TTI block 1 (128 bytes), first 48: 0400 00 01 00 ff 00 0a 00 01 05 0a 00 04 00 14 02 00 ................ 0410 80 47 6f 6f 64 20 65 76 65 6e 69 6e 67 2e 81 8f .Good evening... 0420 8f 8f 8f 8f 8f 8f 8f 8f 8f 8f 8f 8f 8f 8f 8f 8f ................ TTI block 2, first 48: 0480 00 02 00 ff 00 0a 00 04 0a 0a 00 07 0f 14 02 00 ................ 0490 54 6f 6e 69 67 68 74 3a 20 74 68 65 20 63 61 66 Tonight: the caf 04a0 c2 65 20 74 68 61 74 20 6e 65 76 65 72 8a 8a 63 .e that never..c
1 00:00:01,200 --> 00:00:04,000 <i>Good evening.</i> 2 00:00:04,400 --> 00:00:07,600 Tonight: the café that never closes, and the rain that won’t. 3 00:00:08,000 --> 00:00:11,200 First, the weather.
What is an EBU STL file?
The European Broadcasting Union’s format for exchanging subtitles between broadcasters and subtitling companies. It’s binary: a 1,024-byte header with the frame rate, alphabet and programme details, then a 128-byte block for each subtitle, holding its number, time in, time out, position and text.
- Frame rate
- What it holdsSTL25.01 or STL30.01
- In the SRTTurns frames into milliseconds
- Character table
- What it holdsLatin, Cyrillic, Arabic, Greek or Hebrew
- In the SRTLetters and accents decoded
- Programme start
- What it holdsA timecode such as 10:00:00:00
- In the SRTTimes counted from it
- Time in and out
- What it holdsHours, minutes, seconds, frames
- In the SRTThe caption’s times
- Text field
- What it holdsText, new-line, italics and colour codes
- In the SRTLines, with italics and underline kept
- Comment flag
- What it holdsNotes not meant for broadcast
- In the SRTLeft out
| Part | What it holds | In the SRT |
|---|---|---|
| Frame rate | STL25.01 or STL30.01 | Turns frames into milliseconds |
| Character table | Latin, Cyrillic, Arabic, Greek or Hebrew | Letters and accents decoded |
| Programme start | A timecode such as 10:00:00:00 | Times counted from it |
| Time in and out | Hours, minutes, seconds, frames | The caption’s times |
| Text field | Text, new-line, italics and colour codes | Lines, with italics and underline kept |
| Comment flag | Notes not meant for broadcast | Left out |
Why do STL times start at 10:00:00:00?
Broadcast tapes and files often start their timecode at 10 hours, and the STL’s times follow the programme’s timecode. The file records that start, so the converter counts from it and your first subtitle lands near 0:00 in the SRT, matching a video file that starts at zero.
If your video keeps the broadcast timecode, untick Count times from the programme start, and the SRT keeps the original times. Still off by a few seconds? Move every subtitle with the subtitle shifter.
What happens to teletext colours and double height?
They’re dropped. EBU STL files for teletext carry colour, background and double-height codes; SRT has no place for them, so each becomes a space between words where it sat. The words, line breaks, italics and underline are kept.
Cumulative subtitles, where a second part is added under the first while it’s still on screen, become one SRT caption per step, so each shows what viewers saw at that moment.
What if the STL file is text, not binary?
Then it’s a Spruce STL, DVD Studio Pro’s subtitle format, which shares the extension. Its lines read like “00:00:31:02 , 00:00:33:00 , text”. The converter reads those too, but the file doesn’t say its frame rate, so choose your video’s from the list.
Opening a binary EBU STL in a text editor shows mostly symbols: that’s expected, and the file is fine.
How do you make subtitles when there’s no STL at all?
From the recording itself. NoteOwl transcribes recordings you import on your Mac with on-device AI models, names each speaker and saves an SRT file timed to the speech. Nothing is uploaded.
FAQ
Questions about converting STL to SRT
How do I open an EBU STL file?
It’s a binary file, so a text editor shows symbols rather than words. Convert it here instead: the STL to SRT converter decodes the subtitles and shows them with their times, ready to read or save.
Why are my converted subtitles ten hours late?
The STL’s times follow a broadcast timecode that starts at 10:00:00:00. Leave Count times from the programme start ticked, and the converter subtracts that start so the first subtitle lands near 0:00.
Does it read accented letters and other alphabets?
Yes. Latin files write accents as a separate byte before the letter, and the converter joins them, so é, ü and č come through. Cyrillic, Greek, Arabic and Hebrew files are read with their own character tables.
Can I convert STL to VTT?
Yes. After adding the file, choose VTT above the result. You get a WebVTT file with the same subtitles and times, for a web player.
Can it convert SRT to STL?
No. This page reads STL files and writes SRT, VTT or text. Many editing apps can import the SRT it saves.
Is my STL file uploaded?
No. The converter runs in your browser: the file’s bytes are read and decoded on your device, and nothing is sent anywhere.
Keep exploring
More subtitle converters
- Subtitle converterConvert subtitles between SRT, VTT, SBV and ASS, or to plain text, in your browser; SSA scripts and meeting transcripts work too
- SRT to VTT converterConvert SRT to VTT, VTT to SRT, or either to clean text with each speaker’s lines merged, in your browser; Zoom and Teams transcripts work
- VTT to SRT converterConvert a WebVTT file to SRT in your browser: times rewritten, cue settings and styling blocks dropped, voice tags kept as names
- SRT to TXT converterTurn an SRT subtitle file into plain text: numbers and timestamps removed, broken lines joined into paragraphs
- VTT to TXT converterTurn a VTT file, such as a Teams or Zoom meeting transcript, into clean text with each speaker’s turns as paragraphs
Related
- SCC to SRT converterConvert a Scenarist SCC (CEA-608) caption file to SRT, VTT or text in your browser: pop-on, roll-up and paint-on captions read frame by frame
- Subtitle shifterMove every caption in an SRT, VTT, SBV or ASS file earlier or later, or re-sync it from two points; only the times change
- Online subtitle editorEdit an SRT or VTT file in your browser: change text and times, add and delete captions, catch overlaps and over-fast captions, download
Subtitles from your own recordings, on your Mac
Free to download. Runs entirely on your Mac.
macOS 26 or later · Apple Silicon (M1 or newer) · 16 GB memory minimum, 24 GB recommended
About NoteOwl
NoteOwl is private AI meeting notes and memory for the Mac. It captures meetings without a bot joining the call, labels every speaker, writes summaries and action items, and builds a memory of every conversation that you can chat with — fully offline, because the speech recognition and the AI run on the Mac itself. Dictation into any app is free; Pro is a one-time purchase.
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