What this tool does
This one page actually covers three jobs: merging an original and a translated subtitle file into one bilingual file, adjusting the order and style of a file that is already bilingual, and adding special effects to a single-language file. All three share the same style parameters and the same preview.
- Merge two files — you have an original and a translation; combine them into one bilingual file and export it.
- Adjust a bilingual file — it is already bilingual but the order or the styling is wrong; lay it out again.
- Single-language file — only one file; give it a font, an outline, a position.
- Switch between the three with the tabs on the left; the style panel and the preview are shared.
Three jobs, one page
The top of the page has three tabs: Merge two files, Adjust a bilingual file, Single-language file. Your choice decides how many input columns appear on the left.
When merging two files, the left side holds two columns, "1 Original subtitles" and "2 Translated subtitles"; each accepts an uploaded file or text pasted straight in. Adjusting a bilingual file and styling a single-language file each need only one column.
How two files are paired
The first item under "3 Merge settings" is the pairing mode: Pair by order · use the original timeline, Pair by timeline · use the original timeline, Pair by order · use the translated timeline.
When both files have the same number of entries in the same order, pairing by order is the safest. When the counts differ (one side merged entries, the other split them), pair by timeline and let the tool match by proximity. Whose timeline to use depends on which file is more accurate — usually the original.
Below that are the text structure (auto-detect / two lines per entry / alternating pairs) and the order (original on top / translation on top).
Adjust the style item by item
The style panel sits on the right. When you export ASS, the "ASS appearance" block applies: layout (split · separated top and bottom / stacked · two lines at the bottom), the size, colour, opacity, font, bold, italic, letter spacing, outline, outline colour, shadow/background (none / shadow / background), depth, border colour, border opacity, horizontal alignment (bottom · left / bottom · centre / bottom · right) and distance from the bottom of the translation (primary) line, plus the font, shadow/background and left/right margins of the original (secondary) line.
When you export bilingual VTT styling, the "WebVTT style" block applies: on top of six presets (standard / compact / cinematic / top / accessible / portrait) you can change the vertical line, the anchor (bottom / top / centre), the horizontal position, the width size, the align value and the line height of the whole cue, plus the background colour, background opacity and outline width of the translation line; the original line can inherit the main style or be set separately.
When you are done you can save the result as a preset and reuse it later by selecting it under "From saved presets" and clicking "Apply".
Check the preview before exporting
"Merge preview" is a table: #, time, original, translation, style. The bar above filters suspect rows by "has sound effects", "has a speaker prefix", "shorter than 1 second", "more than two lines" and "reading speed exceeded", or by a keyword you type.
Clicking the style slot of a row expands that slot's editor and lists only the rows using it; "Clear all overrides" returns every manual override to the template. The timeline adjustment area below handles a global offset (from a given cue) and proportional scaling.
Once it looks right, go to "4 Export": download the subtitle file or copy its contents.
What is left untouched
Styling changes appearance only, never dialogue. The text of the original and the translation is not altered by a single character during the merge; unless you deliberately change it in the adjustment area below the preview, the timeline comes from the file you chose.
When you export SRT or "VTT without styling", no style information is written into the file — the page tells you that the VTT has no STYLE block and the player will use its default appearance. If you want styling, choose bilingual VTT styling or ASS.
Common questions
What if the two files have different entry counts? Use "Pair by timeline" and the tool matches by proximity; entries it cannot match are not invented.
What if a player ignores the styling in an exported ASS? The styles are stored inside the file, but player support for ASS varies. If you need a more portable look, export bilingual VTT styling.
How do I get back to the initial template after messing it up? "Restore default parameters" in the ASS block and "Restore template defaults" in the VTT block each reset their own section.
What are the seven rows in the sample? They are a built-in example, only there so you can see what a merge looks like; the sample cannot be exported. Upload your own subtitles and click the merge preview and they are replaced automatically.
Privacy
Subtitles are processed entirely in the browser: nothing is uploaded and nothing goes through a server. Close the browser and everything from that session is gone.
Related tools and guides
To split a bilingual file back into two tracks use Bilingual split; to go the other way and turn a single language into a bilingual file see Two ways to make bilingual subtitles; run the result through Subtitle QC; for a whole season at once use Batch conversion.