SyncMySubsConvert SRT to EBU STL
Turn an SRT file into an EBU STL .stl file (EBU Tech 3264), the binary subtitle format used in European broadcast. It writes the 1024-byte GSI header and one 128-byte TTI block per subtitle, at 25 fps with ISO 6937 text. Drop your SRT below; it builds the binary in your browser, nothing is uploaded.
New to these formats? Broadcast caption formats explained →
Writes a standard EBU STL (EBU Tech 3264) file: a 1024-byte GSI header and 128-byte TTI blocks, 25 fps, Latin (ISO 6937) text, centred and white. Colours, boxing, italics and exact on-screen positioning are not encoded, and timecodes start at 00:00:00:00. This is the common interoperable subset, not the full spec.
SRT to EBU STL
EBU STL (the .stl defined by EBU Tech 3264) is the subtitle exchange format long used by European broadcasters. It's binary, not text: a fixed 1024-byte General Subtitle Information (GSI) block describing the file — frame rate, character table, counts, timecodes — followed by a 128-byte Text and Timing Information (TTI) block for each subtitle, carrying the in/out timecodes and the text.
This tool writes a clean, standard file: 25 fps (the European norm), the Latin ISO 6937 character table, centred white subtitles, one TTI block per cue with a newline between rows. Accented Latin characters are encoded using ISO 6937's combining-diacritic scheme, so names and European-language text come through.
It writes the common interoperable subset, so styling and exact positioning aren't encoded — the page lists what's carried and what isn't. To read an STL back into SRT, use EBU STL to SRT.
FAQ
Is this the EBU STL binary format, or the Spruce text .stl?
This is EBU STL (EBU Tech 3264), the binary broadcast format with a GSI header and TTI blocks. The Spruce Subtitle File also uses the .stl extension but is an unrelated text format — this tool does not write that.
What frame rate and character set does it use?
25 fps and the Latin ISO 6937 character table, the European broadcast norm. These are written into the GSI header so a conforming STL reader interprets the timecodes and text correctly.
Are colours, boxing and positioning included?
No. It writes centred white subtitles — the interoperable core. Teletext colours, boxing, italics and precise row positioning aren't encoded. What is and isn't carried is stated on the page.
What if a subtitle is very long?
Each subtitle is written as a single 112-byte TTI text block. A cue longer than that is truncated and flagged after conversion; keep cues to roughly two rows of 40 characters, as subtitling guidelines recommend anyway.
Is my file uploaded anywhere?
No. The STL binary is assembled in your browser. Your file never leaves your device and no server is involved.