Free online TXT to SUP converter

Blu-ray authoring software and some players require subtitles as SUP files rather than editable text. Converting a timed TXT subtitle file renders each caption as a bitmap for more predictable display on Blu-ray-compatible devices.

What the TXT format is

In video subtitles, TXT is usually a plain-text file containing dialogue and timing data, although .txt is not a standardized subtitle format. It may contain SRT-style blocks, for example:

00:00:12,000 --> 00:00:15,500
Welcome to the film.

Subtitle editors, media players, transcription software, and script tools use these files. Some use frame numbers instead of timestamps, while others contain only one dialogue line per entry. A TXT file containing unsynchronized prose cannot produce correctly timed SUP subtitles until start and end times are added manually.

What the SUP format is

For video subtitles, SUP generally means a Blu-ray Presentation Graphic Stream (PGS) file. It stores each caption as a timed bitmap image, including its text, colors, transparency, and position, rather than as editable characters.

Bitmap subtitles preserve the rendered appearance across Blu-ray authoring tools and compatible players, support outlines and non-Latin scripts, and allow precise positioning. They are less convenient to edit than text subtitles: changing a word requires regenerating the affected graphic. SUP files are also normally much larger than TXT, SRT, or WebVTT files.

How to convert TXT to SUP

Subtitle Edit is a practical desktop option for creating Blu-ray SUP output.

1. Open Subtitle Edit and use File → Open to load the TXT file. If Subtitle Edit asks for a format, select the syntax used by the file, such as SRT or a frame-based format.
2. Check the character encoding. Use UTF-8 when the subtitles contain accented characters, Asian scripts, or other non-ASCII text.
3. If the file contains dialogue without timestamps, add start and end times for every caption before exporting. Review overlaps, gaps, reading speed, and line breaks.
4. Choose File → Export → Blu-ray sup. The exact capitalization and menu wording can vary by Subtitle Edit version; select the Blu-ray SUP or PGS export option if a separate export dialog appears.
5. Set the target video dimensions and subtitle appearance, including font, size, color, outline, alignment, and vertical position. Use the resolution required by the Blu-ray authoring project, commonly 1920×1080 for HD video.
6. Export the file with a name such as movie.sup. Test it in the intended Blu-ray authoring application or another player that supports Blu-ray PGS subtitles.

You can also convert the file on 101convert.com without installing software. The source must still contain valid timing data, and the available font, resolution, and compatibility settings depend on the converter.

Quality and compatibility limitations

• A prose TXT file does not provide synchronization, caption duration, speaker changes, or reliable line breaks. Prepare and proof those elements in a subtitle editor first.
• SUP captions are rasterized during export. Changing the font or increasing the resolution later cannot improve an existing SUP file; export it again with the required settings.
• PGS uses bitmap palettes and transparency. Check outline contrast, transparent backgrounds, safe-area placement, and special characters because authoring tools and players may render them differently.
• Confirm that the destination accepts Blu-ray PGS SUP. DVD subtitle SUP files and text formats such as SRT are different formats and are not interchangeable.