Subtitle Editor

Edit, Synchronize, and Convert SRT and WebVTT Subtitles Online

The Subtitle Editor is a browser-based caption timing and editing workspace for video editors, translators, localization teams, and content creators. It parses both SubRip (.srt) and W3C WebVTT (.vtt) subtitle files directly in your browser, allowing you to shift timestamps, fix frame-rate drift, split or merge cues, run batch find-and-replace across thousands of lines, preview captions against a local video file, and export clean files without uploading media to a server.

If you only need a direct one-click format conversion, you can also use our dedicated SRT to VTT, VTT to SRT Converter, SRT to CSV, CSV to SRT Converter, SRT to XLSX, and SRT to Text tools.

How to Use the Subtitle Editor

1. Load your subtitle file: Paste SubRip (.srt) or WebVTT (.vtt) text into the Input Subtitles editor, or click the upload icon to open a local file from your device.
2. Shift or scale timestamps globally: Use the Time Shift Offset field (in milliseconds) or the quick -500 ms / -100 ms / +100 ms / +500 ms buttons to fix constant audio-caption delay. If captions drift progressively over a long video, select a Frame Rate Conversion Preset or enter a custom Speed Scale Factor.
3. Clean and format cues: Toggle Strip HTML & Style Tags to remove <i>, <b>, and ASS override tags (such as {\an8}), or keep Renumber Cues Sequentially enabled to repair broken index numbers.
4. Edit individual cues on the timeline: Use the Interactive Cue Timeline to edit start times, end times, and caption text inline. Click Split to divide a long cue at its midpoint timestamp, Merge Next to combine two consecutive cues, or -100ms / +100ms to nudge a single line.
5. Preview with video and export: Optionally select a local video file under Video & Timestamp Caption Preview to verify synchronization in real time, choose your target Output Format (.srt, .vtt, or plain .txt), and copy or download the finished file.

Understanding Subtitle Synchronization: Constant Offset vs. Frame-Rate Drift

Out-of-sync subtitles typically fall into one of two mathematical categories:

• Constant Offset (Linear Shift): Every subtitle appears a fixed amount of time too early or too late (for example, 1.5 seconds late because a studio intro was removed). Adding -1500 ms or +1500 ms shifts every start and end timestamp by the exact same offset: T_new = T_old + Offset.
• Frame-Rate Drift (PAL vs. NTSC Speedup): Subtitles start in sync at the beginning of a film but drift further apart every minute. This happens when captions timed for a 23.976 fps (NTSC cinema) video are played on a 25 fps (PAL broadcast) release, or vice versa. Applying the linear transformation T_new = (T_old * ScaleFactor) + Offset rescales every cue proportionally so captions stay locked from opening scene to end credits.

Supported Subtitle Standards and Formats

• SubRip (.srt): The universal plain-text subtitle format supported by VLC, DaVinci Resolve, Adobe Premiere Pro, Final Cut Pro, YouTube, and hardware media players. Uses sequential integer cue numbers and HH:MM:SS,mmm --> HH:MM:SS,mmm timestamps with a comma decimal separator.
• WebVTT (.vtt): The W3C Web Video Text Tracks standard required by HTML5 <track> elements and modern web players. Begins with a WEBVTT header and uses a period (.) before milliseconds (HH:MM:SS.mmm).
• Plain Text Transcript (.txt): Strips all sequence numbers and timecode headers to produce clean, line-by-line spoken dialogue suitable for show notes, articles, or VTT to Text Converter workflows.

Privacy and Client-Side Performance

All subtitle parsing, timestamp arithmetic, find-and-replace operations, and video previews execute 100% locally in your browser using JavaScript and the HTML5 File and URL.createObjectURL APIs. Even multi-hour feature film scripts with 8,000+ lines are processed in memory with paginated timeline rendering, and your subtitle files and video files are never uploaded to any external server.