SubFly

About

Updated 21 October 2026

SubFly translates subtitle files with AI - and gives them back with every timestamp, style and sign exactly where it was.

What it does

You upload SRT, ASS, SSA or VTT subtitles, choose a target language and a translation style, and SubFly translates the dialogue with Google's Gemini models. Only the dialogue text is sent for translation; timings, line counts, ASS styling, typeset signs and karaoke stay exactly as uploaded, so the translated file drops straight back into your video.

On top of that sit the tools a long project needs:

  • Projects that keep a whole season's files and translations together.
  • A word list so character names and terms are translated the same way in every episode.
  • Style presets and a prompt library - including a Hinglish fansub rulebook - so the tone stays consistent.
  • Side-by-side review with find and replace, to polish the result before you publish it.
  • Resumable jobs that save every finished batch, so a failure never costs you work already done.

Who it's for

Fansub teams, independent creators, translators and anyone localising video into another language - from a single YouTube video to a fifty-episode series. Our guides cover subtitle formats, timing, readability and translation style, whether or not you use SubFly.

How we work

  • Timing is untouchable. Every cue keeps its original start and end time. A batch that comes back with the wrong number of lines is retried, never stitched together.
  • Your files are yours. We don't sell your data, and we don't use your subtitles to train AI models. You can delete projects at any time.
  • Keys stay secret. API keys are encrypted with AES-256-GCM and are never shown again after you save them.
  • Honest about AI. AI translations are fast and usually good, but they can be wrong. We build tools for reviewing them, and we recommend a human review before anything is published.

Who runs it

SubFly is built and run by SubFly. Questions, feedback and partnership requests are always welcome - see Contact for every way to reach us, or write to our support address.