Make dual language subtitles from one file, or join two you already have

Why dual subtitles trip up general AI assistants

Asking a chatbot for subtitles in two languages doubles the hardest part of subtitle work. It has to write out every block of the file, number and time code included, and now each block holds twice the text. On a feature film the reply runs out long before the end, so the assistant stops, asks you to continue, or shortens the last part. Along the way it may join two short lines, renumber blocks or retype a time code wrong, and the subtitles drift away from the speech.

Placement is the second problem. Showing one language at the top of the screen needs a different code in each format, and a player ignores a code it does not understand. An assistant writing plain text rarely gets this right for every line.

This tool never asks a model to write the file. When it translates, it sends only the text, in blocks of up to 60 lines, requires each line back under its own number, asks once more for any line that is missing, and keeps the original if it is still missing. The timings are copied from your file, and the layout codes are written by the tool.

Two ways to get the second language

Translate: upload one file and pick a language. Every line is translated, and the original and the translation are shown together on the original timing. An .ass or .ssa file works too; it is read as text, so italics and a position code are kept but the original styling is not.

Join: upload two files you already have, for example film.en.srt and film.fa.srt. No AI model is used. Each line of the second file is attached to the line of the first file it overlaps most in time, so two short lines that fall within one longer line both appear with it. A line of the second file that overlaps nothing keeps its own timing and shows on its own, in the second language only. Joining is free in full up to 3000 lines.

What people use dual subtitles for

• Learning a language from films and series, with the familiar language as a safety net
• Families where parents and children read different languages, watching together
• Couples and friends who do not share a first language
• Teachers preparing a film for a class of mixed language levels
• Combining an official subtitle file with a fan translation in another language

Limits and getting a good result

Joining depends on timings. Two files made for the same release line up well; files from different releases, or one that runs a few seconds early, pair the wrong lines. Fix the timing first with the Fix Subtitle Sync tool, then join. When translating, the result follows the timings of your file, so start from one that matches your copy of the video.

Some players ignore {\an8} in SRT files and show both languages at the bottom. If that happens, choose stacked, or download VTT or ASS, which place the top line in their own way. Two languages take more room than one, so stacked subtitles can cover more of the picture on small screens.

Translation is done by a machine. It is well suited to learning and watching at home; for teaching material or a public screening, have a person check the second language.