Subtitle Editor
Fix the timing and wording of SRT, VTT and SMI subtitles and convert between them; legacy Korean EUC-KR files are read correctly.
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Subtitle Editor: complete guide
Walk through the steps and examples, or jump straight to the topic you need.
At a glance
- Supported formats
- Reads SRT, VTT and SMI (SAMI) and saves them in any of the three. For SMI, the Korean (KRCC) language track is picked first.
- Limits
- Files up to 2 MB and 20,000 subtitles are read. If a file exceeds that, you are told how far it was read.
- Encoding
- Reads as UTF-8 first and, if the text is garbled, re-reads it as an older Korean encoding (EUC-KR or CP949). It cleans up the BOM and CRLF line endings and leaves line breaks inside the text as they are. Saving defaults to UTF-8, and SRT and SMI can also be saved as EUC-KR.
- Skipped parts
- Blocks with no timing line or an unreadable time are not dropped silently; they are listed for you.
- Timing tools
- Shift all (in seconds or frames), match speed with two reference points, change frame rate (23.976, 24, 25, 29.97, 30, 60), fix overlapping times and sort by time.
- Checks
- Flags subtitles whose end is before the start, subtitles that overlap the previous one, subtitles shorter than 0.3 seconds, and text over 500 characters.
- What it does not do
- It does not listen to video or audio to create new subtitles.
- Where it runs
- Reading, editing and saving all happen in this browser.
How to use Subtitle Editor
Upload a subtitle file
Drag and drop an SRT, VTT or SMI file, or choose one. The format is detected from the file contents. If some parts could not be read, you are told which ones.
Pick the tool that matches the drift
If everything is consistently off, use Shift timing; if the gap grows toward the end, use Match speed with two reference points. If subtitles overlap, Fix overlaps pulls back only the end of the earlier subtitle.
Fine-tune text and timing
You can edit each subtitle's start and end times and its text directly. Subtitles with problems are marked with an outline and a note, so start by checking those.
Choose a format and save
Saving as SRT renumbers the subtitles from 1, saving as VTT adds a WEBVTT marker at the top, and you can save as SMI too. For older players you can save SRT or SMI as EUC-KR, and Copy all is available as well.
What it’s good for
When the whole subtitle file is out of sync
If the subtitles are consistently early or late, use Shift timing to move them all at once. Enter the amount in seconds; a negative value pulls them earlier. If they drift further apart toward the end because the video length differs, use Match speed with two reference points. Give the time a particular subtitle should actually appear, and the tool stretches or shrinks the whole timeline in proportion to match.
What is the difference between SRT and VTT
SRT numbers every subtitle and uses a comma in timestamps. VTT starts with a WEBVTT marker at the top of the file and uses a period in timestamps. Web video players usually require VTT, while desktop players often use SRT. This tool reads both formats, plus SMI (SAMI), which has long been used in Korea, into the same structure and lets you convert between them. We also checked by round trip that times and text stay intact after converting and saving.
Worked examples
When subtitles are 1.5 seconds early
Shift all by 1.5
First subtitle 00:00:01,000 --> 00:00:03,50000:00:02,500 --> 00:00:05,000Matching speed with two reference points
The subtitle currently at 00:00:10,000
should actually appear at 00:00:11,00010-second subtitle → 11 seconds
20-second subtitle → 22 secondsWhich tool fits which kind of drift
Swipe the table sideways to see the rest.
| Symptom | Tool to use | Watch out for |
|---|---|---|
| Off by a constant amount from start to end | Shift timing | Enter the value in seconds; a negative value pulls earlier. |
| The gap grows toward the end | Match speed with two reference points | You need to know exactly when the subtitle should really appear. |
| Subtitles overlap and show together | Fix overlaps | Only the end of the earlier subtitle is pulled back; the text is not changed. |
When the result isn’t what you expected
It says no subtitles were found
Only SRT, VTT and SMI are read. Other formats such as ASS are not supported. Open the file in a text editor and check that SRT and VTT timing lines contain an arrow (-->) and that SMI contains SYNC Start tags.
Some subtitles are missing
Blocks with no timing line or a broken time format are not read and are listed instead. Check the parts named in the notice in the original file, fix them and upload again.
Korean text looks garbled
UTF-8 and the older Korean encodings (EUC-KR and CP949) are detected automatically. If the text is still garbled, it may be in another country's encoding, so re-save the file as UTF-8 in an editor and upload it again. If the saved file looks garbled on an older player, try saving as EUC-KR.
The saved subtitles do not show in my player
Check the format your player requires. Web video usually uses VTT and desktop players use SRT. Some players load the subtitles automatically if the file name matches the video's.
Key terms
- SRT
- The most widely used subtitle format, with a number, a time range and text separated by blank lines.
- VTT
- A subtitle format for web video. A WEBVTT marker is placed at the top of the file.
- Sync
- How well the time a subtitle appears matches the time the line is actually spoken.
Subtitle Editor FAQ
Does it create subtitles automatically?
No. It is a tool for fixing the timing and text of a subtitle file you already have. It does not include a feature that listens to speech and transcribes it.
How does it handle overlapping subtitles?
It only pulls the end time of the earlier subtitle back to just before the next subtitle starts. The text is not touched, and the end is kept from falling before the start after tidying.
Is my file uploaded?
No. Reading, editing and saving all happen inside this browser.
Can I merge two subtitle files?
For now, one file at a time. You can add rows with Add subtitle and enter text by hand, but there is no feature to merge two files automatically.
Can I sync while watching the video?
Video playback is not provided. Use the times you check in your player in Match speed with two reference points.
Are my edits saved?
No. Refreshing the page returns it to the original state, so save a file when you finish.