AI Subtitle Studio
Free tool

Online subtitle editor

Open an SRT, WebVTT or ASS file — or a video with subtitles inside it — and fix it right here: correct typos and timing, split and merge lines, find and replace, add italics or colour, with the video playing beside it. Your files never leave your browser.

  • Edited in your browser — never uploaded
  • Free, no account, no watermark
  • Opens MKV, MP4, WebM and MOV videos
  • ASS styles and signs kept intact

Files are opened by your browser and stay on your device — even a multi-gigabyte video is never uploaded. Nothing you type is sent to us.

Shift subtitles

Move the selected subtitles earlier or later, keeping their spacing. Seconds or a timestamp; a minus sign moves them earlier. Nothing moves before 0:00.

Check the subtitles

Clean up the subtitles

consecutive repeats before dropping the rest

Move subtitle position

Pick where the subtitles sit on screen. SubRip gets an {\an8}-style tag, which VLC, mpv and other libass players read; WebVTT gets real cue settings.

Apply to

Reading video…

How it works

Edit a subtitle file in three steps

Open your file

Drop in an SRT, WebVTT or ASS/SSA file, a video with subtitles inside it, or start a new file from scratch. It opens in your browser — nothing is uploaded.

Fix text and timing

Click a line to edit it. Change times, split and merge lines, search and replace across the file, and add italics or colour.

Download the result

Save in the format you opened, or export to SRT, WebVTT, ASS or plain text. Your changes are written as UTF-8.

What you can do

Everything a subtitle editor needs, in a browser tab

Fix text and typos

Every line is an editable field. Line breaks, punctuation, speaker dashes — type them as you want them on screen.

Adjust timing precisely

Type start and end times to the millisecond, nudge them with the arrow keys, or shift a whole selection earlier or later.

Split and merge lines

Split a long subtitle at the text cursor — the timing is divided to match — or merge several short ones into one.

Find and replace

Filter the list as you type, then replace every match at once — with match case and whole-word options that understand accented letters.

Italics, bold and colour

Format selected words or whole lines. Written as <i> and <font> tags in SRT and VTT, and as override tags in ASS — with a live preview.

Catch problems early

Lines that overlap the next one or flash by too fast to read (over 25 characters per second) are marked, and one button jumps between them. Check & fix goes further — line length, gaps, markup — against a style guide, and repairs it in one undoable step.

Clean up in one pass

Strip [sound descriptions], subtitle-site credits, ads and speaker labels; repair mangled characters and OCR misreads. You see what it would remove before it does, and Undo puts it back.

Move subtitles on screen

Put them at the top, in a corner or in the middle — clear of burnt-in captions or a player's controls — for the lines you select or the whole file.

Edit against the video

Open an MKV, MP4, WebM or MOV, pick the subtitle track inside it, and time lines with the picture playing beside the list. The video is never uploaded.

Formats

SRT, WebVTT and ASS — edited the way each one works

SRT (SubRip) is the format most players, TVs and streaming apps read. The editor renumbers the subtitles for you on save, so deleting or inserting lines never leaves gaps or duplicates in the numbering.

WebVTT is what HTML5 video players and YouTube use. The header, style blocks and each cue's position settings are kept when you save as VTT again.

ASS/SSA files carry their own fonts, colours and typesetting. Instead of rebuilding the file — which would flatten every style to plain white Arial — the editor changes only the lines you edited and leaves the rest of the script byte-for-byte as it was. Signs keep their \pos, and karaoke stays in time.

Need a format the editor doesn't open, like MicroDVD, SAMI or SBV? Convert it first with one of the free format converters, then open the result here.

Keyboard shortcuts

Work through a file without the mouse

Ctrl/⌘ + SDownload the file in its own format
Ctrl/⌘ + ZUndo (Shift, or Ctrl + Y, to redo)
↑ / ↓Move between subtitles (Shift extends the selection)
EnterStart typing in the selected subtitle
EscCancel what you typed, or clear the selection
Click · Shift-click · Ctrl/⌘-clickSelect one, a range, or add to the selection
Ctrl/⌘ + ASelect every subtitle shown
DeleteDelete the selected subtitles
Ctrl/⌘ + B / I / UBold, italic, underline — the words selected, or whole lines
Alt + ← / →Move the selected subtitles 0.1 s (Shift: 1 s)
↑ / ↓ in a time fieldNudge that time 0.1 s (Shift: 1 s)
More free tools

Fixing the whole file at once?

Shift Timing

Every subtitle early or late by the same amount? Move the whole file in one go.

Cleanup

Strip SDH sound descriptions, credits, ads and speaker labels in one pass.

Translate subtitles

Translate an SRT, VTT or ASS file into another language with AI, timing intact.

Subtitle Checker

Find every overlap, flicker-short gap, long line and fast subtitle in a file — and fix them in one click.
Prefer not to upload your file?

The AI Subtitle Studio desktop app has this same Tools section built in — plus AI transcription, translation and batch processing for a whole season at once, all running locally on your Mac or PC.

Get the desktop app
FAQ

Questions about the subtitle editor

Is the online subtitle editor free?
Yes. There is no account, no limit on how many files you edit, and no watermark. It runs in your browser, so it costs us nothing to run.
Is my subtitle file or video uploaded?
No. A subtitle file is read, edited and saved entirely in your browser, and a video is only looked at by your browser too — neither ever reaches our servers. Unsaved work is kept in your browser's own storage so a closed tab doesn't lose it, and you can discard it at any time.
Can I open a video and edit the subtitles inside it?
Yes. Open an MKV, WebM, MP4 or MOV file and the editor lists the subtitle tracks inside it. Pick one and it opens like any subtitle file, with the video playing beside it. Only text subtitles (SubRip/SRT, ASS/SSA, WebVTT and mov_text) can be edited; the video itself is not changed, so you download the subtitles as a separate file.
Why does my video list a subtitle track I can't open?
Blu-ray and DVD discs store subtitles as pictures (PGS, VobSub, DVB), not text, so there are no words to edit. Turning them into text needs OCR. The AI Subtitle Studio desktop app can transcribe the audio instead and give you a fresh, editable subtitle file.
The video won't play, but the subtitles opened. Why?
Playback is up to your browser. Chrome and Edge play most MKV, MP4 and WebM files; Firefox and Safari play MP4 and WebM but usually not MKV, and no browser plays every video codec (HEVC/H.265 is the usual culprit). The subtitles are read from the file directly, so you can still edit them — you just won't see the picture.
Which subtitle formats can I edit?
SubRip (.srt), WebVTT (.vtt) and Advanced SubStation Alpha (.ass and .ssa). You can save in the format you opened, or export to SRT, WebVTT, ASS or plain text.
Does editing an ASS file keep its styles?
Yes. An ASS or SSA file is edited in place: the [Script Info] and [V4+ Styles] sections, every line's style, layer, margins and effect, and every line you didn't touch are written back exactly as they were. Karaoke and vector-drawing lines are kept but not shown, so they can't be broken by accident.
How do I change subtitle timing?
Type a new start or end time, or use the arrow keys in a time field to nudge it by 0.1 s (1 s with Shift). To move several lines at once, select them and use Shift, or press Alt+← / Alt+→. To move a whole file, the Shift Timing tool is quicker.
What do the warning marks mean?
A line is marked when it overlaps the next one on its track — most players then stack the two or drop one — or when it has more than 25 characters per second, faster than most people can read. In an ASS file, signs and lines on other layers or styles are allowed to overlap dialogue and are not marked. Hover the mark to see which, and use the warnings button to jump between them.
Can I clean up SDH, credits and ads in the editor?
Yes. Tools → Clean up runs the same cleanup as the free Cleanup tool — it strips sound descriptions like [door slams], subtitle-site credits, ads, speaker labels and more, repairs mangled encoding and OCR misreads, and fixes overlapping timing — but on the file in your browser, so nothing is uploaded. It shows what it would remove and change before you apply it, and Undo puts it all back. It works on SRT and WebVTT files, not ASS.
Can I move the subtitles to the top of the screen?
Yes. Tools → Position puts the selected subtitles, or all of them, at the top, a corner or the middle of the frame, or clears positioning again. SubRip files get an {\an8}-style tag, which VLC, mpv and other libass-based players honour; WebVTT files get real cue settings. It works on SRT and WebVTT files, not ASS, which keeps its own styles and positions.
Can I check my subtitles against a style guide?
Yes. Check & fix runs the same checks as the free Subtitle Checker — timing, line length, reading speed, formatting — against a Standard (Netflix-style), Children's or Relaxed preset. Click a line it found to go to it, or fix everything it can in one step. The fix is a single edit, so Undo puts all of it back.
My file shows strange characters instead of letters.
It was saved in an older, language-specific encoding rather than UTF-8. Pick the right one (Turkish, Cyrillic, Central European…) from the encoding menu that appears above the list, and the file is read again. Whatever you open is saved as UTF-8, which every modern player reads.
Can I time subtitles against the video?
Yes, with the video panel: play the video, pause where a line should start or end, and use Start = now and End = now. Clicking a line jumps the video to it. For a waveform and a timeline to time lines by ear, plus AI transcription, translation and automatic sync, use the AI Subtitle Studio desktop app.