Fix, sync and convert subtitles in your browser

What is SubTweak?

SubTweak is a free subtitle tool that runs entirely in your web browser. It opens SubRip (.srt), WebVTT (.vtt), Advanced SubStation Alpha (.ass/.ssa) and plain-text files, fixes their timing, text and encoding, and saves them in any of those formats. Your subtitle and video files never leave your device.

Most subtitle problems fall into three groups: timing (lines too early, too late or drifting), text (garbled characters, overlaps, hearing-impaired notes you don't want) and format (a player or website that needs a different file type). Each has a tool above, and they can be combined — for example, sync a file, remove SDH text and save it as WebVTT in one go.

How to fix subtitle timing online

1. Open your subtitle file. Click Open subtitle file or drop an SRT, VTT, ASS, SSA or TXT file. The encoding is detected and garbled characters are fixed automatically.
2. Fix the timing. Use Shift for a constant delay, Sync with two points for drift, or FPS for a frame-rate mismatch. Load your video to preview the result.
3. Clean up and edit. Fix overlaps, duplicates and hearing-impaired text in one click, or edit any cue by hand.
4. Save in any format. Choose SRT, VTT, ASS or TXT and download a UTF-8 file.

Offset or drift? Pick the right timing fix

What you see	Cause	Fix
Every line is early or late by the same amount	Different intro, logo or recap	Shift
In sync at the start, further off later	Different speed or frame rate	Two-point sync or FPS conversion
Fine, then suddenly off after a point	Cut scene or ad break	Shift from the selected cue onward
Right after pressing your player’s delay keys, but only until you close it	Player delay is not saved in the file	Bake the player delay into the file
Lines flicker or stack on top of each other	Overlapping cues	Fix overlaps

Subtitle tools

• Shift subtitlesAn online SRT shifter: move all subtitles earlier or later by a fixed amount — the fix when every line is off by the same delay from start to finish.
• Sync subtitles (two-point)Two-point sync fixes subtitles that get further out of step as the video plays — the classic sign of a frame-rate or speed mismatch — and any offset at the same time.
• Frame rate converterRescale subtitle times when the subtitle was made for a video with a different frame rate — most often a 23.976 fps film versus a 25 fps PAL release.
• Fix encodingRepair subtitles that show strange symbols instead of accented letters, Cyrillic, Greek, Hebrew, Arabic, Chinese, Japanese or Korean text, and save them as UTF-8.
• Fix overlaps & timing errorsClean up timing problems that make subtitles flicker, stack on top of each other or vanish too quickly — in one click.
• Remove SDH / hearing-impaired textConvert SDH or closed-caption subtitles into plain dialogue subtitles by removing sound descriptions, speaker labels and music symbols.
• Merge subtitle filesJoin subtitles that were split into two parts — the classic CD1 / CD2 release — into a single file for a single video.
• Bilingual subtitlesCombine subtitles in two languages into one file, so both appear on screen together — a favorite for language learners and mixed-language households.
• Split subtitle filesCut one subtitle file into two at a chosen time — to match a video that was split into two parts or to work on a long file in pieces.
• Online subtitle editorEdit the text and timing of every subtitle, preview the result on your own video and save as SRT, VTT, ASS or TXT — all inside your browser.

Format converters

• SRT to VTTTurn a SubRip (.srt) file into WebVTT (.vtt), the format HTML5 video and most web players require. Timing, line breaks and italics carry over exactly.
• VTT to SRTConvert WebVTT (.vtt) captions — from YouTube, Zoom, Vimeo, online courses or HTML5 players — into SubRip (.srt), the format almost every player, TV and editor understands.
• SRT to ASSConvert a SubRip (.srt) file into Advanced SubStation Alpha (.ass) — a starting point for styled subtitles with custom fonts, outlines, colors and positions.
• ASS to SRTConvert Advanced SubStation Alpha (.ass) subtitles — common for anime and fansubs — into plain SubRip (.srt) that plays on TVs, phones, game consoles and video editors.
• VTT to ASSConvert WebVTT (.vtt) captions into Advanced SubStation Alpha (.ass) so you can restyle them or burn them into a video with a consistent look.
• ASS to VTTConvert Advanced SubStation Alpha (.ass/.ssa) subtitles to WebVTT (.vtt) so they work in the HTML5 <track> element, web players and streaming platforms.
• SRT to TXTExtract just the words from a SubRip (.srt) file — a clean transcript for reading, quoting, translation, study notes or feeding into other tools.
• VTT to TXTTurn WebVTT (.vtt) captions — from Zoom or Teams recordings, YouTube, Vimeo or an online course — into a readable plain-text transcript.
• ASS to TXTPull the dialogue out of an Advanced SubStation Alpha (.ass/.ssa) file as plain text — for proofreading, translation or a script-style transcript.
• TXT to SRTTurn a plain text script or transcript into a SubRip (.srt) subtitle file. Each line becomes one subtitle; timestamps in the text are used when they are there.
• TXT to VTTCreate WebVTT (.vtt) captions for an HTML5 video, course or website from a plain text script or a timestamped transcript.
• SSA to SRTConvert SubStation Alpha v4 (.ssa) files — the predecessor of ASS, still common in older releases — into SubRip (.srt).

Guides

• How to Sync Subtitles With a VideoOut-of-sync subtitles almost always have one of two problems: a constant delay or a gradual drift. Work out which one you have, and the fix takes about a minute.
• SRT vs VTT vs ASS: Which Subtitle Format Should You Use?SRT is the universal plain format, VTT is the web standard, and ASS is the styling powerhouse. Here is how they differ and what happens when you convert between them.
• SRT vs VTT: Which One Do You Need?SRT and WebVTT carry the same subtitles with almost the same syntax. What decides between them is where the file is going — and a handful of details that break when you convert.
• Why Subtitles Drift: Frame Rates ExplainedIf subtitles start in sync and slowly slide out of it, the file was almost certainly timed for a version of the video that plays at a different speed.
• How to Fix Garbled Characters in SubtitlesStrange symbols in place of accented letters, Cyrillic, or Chinese almost always mean the file was read with the wrong text encoding. The text is usually still there, and converting it to UTF-8 brings it back.
• How to Add Subtitles to a VideoMost of the time you don't need to edit the video at all: put a correctly named subtitle file next to it, or load it from your player's menu. Here is how for each common setup.
• Subtitle Timing and Readability GuidelinesGood subtitles stay on screen long enough to read, keep pace with the speech, and break into lines that read naturally. These are the typical rules professionals work with.

Frequently asked questions

Is SubTweak free?

Yes. Every tool is free with no sign-up, no file limits and no watermark. The site is supported by advertising.

Are my subtitle and video files uploaded?

No. Files are opened and processed by JavaScript in your browser, on your own device. Nothing is sent to a server, so unreleased or private material stays private.

Which subtitle formats are supported?

SubRip (.srt), WebVTT (.vtt), Advanced SubStation Alpha (.ass), SubStation Alpha (.ssa) and plain text (.txt), in any of the common text encodings. You can save as SRT, VTT, ASS or TXT.

My subtitles are a few seconds early or late. What do I do?

Use Shift: enter the delay, choose Later or Earlier and apply. If the error grows over the course of the video, use Sync with two points or the FPS converter instead.

Why do my subtitles show strange characters?

The file uses an older language-specific encoding. SubTweak detects it automatically and saves the file as UTF-8; if it guesses wrong, pick the encoding from the menu in the file bar.

Can I use it on a phone?

Yes. The tool works in mobile browsers; on iPhone and Android, open subtitle files from the Files app or your downloads.

Does saving to the same format change my file?

Only what you changed. Unedited lines keep their original text and tags — ASS styles and positions, WebVTT cue settings — while times are rewritten in the standard format.