YTSubConverter

YTSubConverter creates styled YouTube subtitles with formatting such as bold, italics, and color.

github.com/arcusmaximus/YTSubConverter
YTSubConverter homepage screenshot

About YTSubConverter

YTSubConverter creates styled YouTube subtitles by converting subtitle files to SRV3/YTT for upload. It primarily converts .ass files made in Aegisub to .ytt, and also converts .sbv to .srt and between .ttml and .ytt. Output can include bold, italic, underline, colors, positioning, karaoke timing, vertical text and ruby text.

It is available for Windows, macOS and Linux. Use is limited by YouTube behavior, including restricted fonts, font-size rules, and that karaoke and transitions require an .ass source.

Key features

  • Converts .ass subtitle files to .ytt for YouTube upload
  • Converts .sbv files to .srt for editing
  • Converts between .ttml and .ytt formats
  • Produces bold, italic, underline, colors, positioning and karaoke timing
  • Offers glow, bevel, soft shadow and hard shadow options
  • Supports vertical text and ruby text
Best for: YouTube creators who prepare subtitles in Aegisub and need to upload them as styled .ytt files.
Good for
  • Available for Windows, macOS, and Linux
  • Approximates Aegisub subtitle appearance on YouTube
  • Enables YTT features not available in YouTube's built-in editor
Watch out for
  • YouTube limits fonts and defaults unallowed fonts to Roboto
  • Font size cannot go below 75% and Android app ignores size settings
  • Karaoke and transitions require an .ass source

YTSubConverter at a glance

Type
Open-source project
Pricing
Not confirmed. Check the site
Platforms
Linux, macOS, Windows
Open source
Yes · Source code
Language
English
Last checked
Oct 5, 2026 · Online when checked
Listed
Oct 5, 2026

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YTSubConverter FAQ

How do I convert .ass to .ytt?
Launch the program, open the .ass file and click Convert. On Windows, you can also drag the .ass file onto the .exe. Both produce a .ytt file ready for upload.
Can I add styling to existing unstyled YouTube subtitles?
Yes. Open the .sbv file downloaded from YouTube's editor, click Convert, then open the resulting .srt file in Aegisub to add styling.
Why convert TTML to YTT if YouTube accepts TTML?
Converting to .ytt gives access to more features and workarounds for YouTube bugs, though karaoke and transitions still require .ass.
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