Split and Merge Subtitles

Signs a line needs splitting, or merging

Most subtitle files have both problems somewhere. Split a line when:

• It holds two sentences, or one sentence plus the start of the next.
• It's flagged as too fast to read and there's no spare time to give it.
• It wraps to three lines on screen and covers a large part of the picture.
• Two people speak inside it, so the second voice begins while the first person's words are still up.

Merge two lines when:

• One is a fragment of a few words, shown for well under a second.
• A sentence is cut in an awkward place, such as between an article and its noun.
• Several tiny lines flicker past in a row where one steady line would read better.

On both sides the aim is the same: lines that follow the rhythm of speech and break at natural points. Subtitle segmentation covers the conventions in depth.

What Split does to the text and the time

Split acts on the selected line and uses the playhead as the cut.

The time

The first part keeps the original start and now ends at the playhead. The second part begins at the playhead and keeps the original end. Nothing is left between them and nothing overlaps.

The text

The editor works out how far through the line's duration the playhead sits, goes the same proportion into the text, and cuts at the nearest space. Split two-thirds of the way through the time and the text breaks close to two-thirds of the way through its characters.

Text without spaces

Chinese and Japanese lines have no spaces to cut at, so the characters are divided at that same proportion. Expect to move a character or two by hand.

Playhead near an edge

If the playhead is outside the line, or within a tenth of a second of its start or end, the line is cut at its midpoint instead.

Very short lines

A line shorter than 0.2 seconds can't be split.

Afterwards the second part is selected, ready for you to check. The text cut is an estimate, because speech doesn't move at an even pace: a pause inside the line shifts where the words actually fall. Read both halves every time.

Splitting a line, step by step

1. Open the editor, load the video, then import the subtitle file or generate subtitles with AI.
2. Click the line in the list or on the timeline. The video jumps to where it starts.
3. Play, and pause just as the first word of the second half is spoken. Shift with Left or Right steps a tenth of a second at a time.
4. Click Split in the toolbar.
5. Read both halves. If a word landed on the wrong side, cut it from one text box and paste it into the other; the times don't change.
6. Look at the warnings under both rows. A half shown for under 0.8 seconds, or still too fast to read, needs more time or fewer words.

Splitting by ear rather than by counting characters gives you the timing for free: the second half starts exactly when its first word is heard.

Merging fragments back together

Merge joins the selected line with the one that comes next in time.

• The merged line starts when the first began and ends when the later of the two ends.
• Any gap between them is absorbed, so the text stays up through the pause.
• The two texts are joined with a line break rather than a space, so the result shows as two lines. For a single line, click into the text and replace the break with a space; long lines wrap on their own.
• Merging the final line of the video does nothing, since there's nothing after it.
• Empty lines don't leave blank rows behind in the merged text.

Merge only looks forward. To attach a fragment to the line before it, select that earlier line and merge from there. Merging again and again stacks text up, and anything past three lines is flagged because it hides too much of the frame.

Undo, redo and second attempts

Every split and every merge is a single undo step. Press Ctrl+Z or Cmd+Z to step back, and Ctrl+Shift+Z, Cmd+Shift+Z or Ctrl+Y to step forward again. Up to 200 steps are kept, and the same history covers typing, timing changes, imports and style edits, so you can try a split, decide it reads worse, and land exactly where you started.

There are two limits. The history lasts only while the page is open: after a reload, the draft saved in your browser restores your lines and style but not the list of steps. And opening a different video starts a fresh history.

When the result looks wrong

• Split or Merge is greyed out. No line is selected; click one first.
• The cut fell in the middle, not where I paused. The playhead was outside the selected line or right at one of its edges. Select the line, play into it and try again.
• One word is on the wrong side. That's the estimate at work. Move the word between the two text boxes; timing is unaffected.
• The merged subtitle sits on two lines. That's the line break Merge inserts. Swap it for a space if one line fits.
• Merge joined the wrong pair. It follows start times, so when lines overlap, the next one in time may not be the one you meant. Undo, sort out the overlap, then merge.
• The merged line is now too fast to read. Two lines' worth of words share the combined time. Trim filler, or undo and split somewhere else.

Three typical repairs

After the lines are right

Your breaks and line lengths carry into everything you export. Export SRT or VTT to keep the corrected file, or render the video with the subtitles burned in. If what's left is about when lines appear rather than how they're divided, changing subtitle timing picks up from here, and the online subtitle editor tours every other tool. Working on a file without its video? Editing an SRT online covers that case. For a first draft worth splitting and merging, try the AI subtitle generator, or subtitles in another language if the audience doesn't speak the original.

About the subtitle editor on this page

Opens

MP4, MOV, M4V, WebM, MKV videos your browser can decode

Subtitles from

AI (from the speech, optionally translated into one of 21 languages), an SRT or VTT file, or typing them in

You download

An MP4 with the subtitles drawn into the picture at the original resolution and frame rate, plus SRT and VTT files

Cost

Editing, styling, rendering and SRT/VTT export are free, with no account and no watermark. AI subtitles cost 1 credit per minute (5-credit minimum per video); signing in with Google gives 100 free credits and accounts get 10 free credits a day

Privacy

The video never leaves your device and is rendered in your browser. Only for AI subtitles is the audio sent, over HTTPS, and it is deleted within 30 minutes of delivery

Rendering needs

Chrome or Edge 94+, Safari 16.4+, or Firefox 130+ on a computer. Editing and SRT/VTT export work in any current browser