Video Subtitles
Add or edit subtitles for video files. Create SRT subtitle files, sync timing & customize appearance. Make videos accessible to all viewers.
About Video Subtitles
How to Add or Extract Subtitles in 30 Seconds
Adding Subtitles
- Upload your video file (MP4, AVI, MOV, MKV, WebM)
- Upload your subtitle file (SRT, VTT, ASS, SSA)
- Select subtitle position and styling (optional)
- Click "Burn Subtitles" to embed permanently
- Download your video with hardcoded subtitles
Extracting Subtitles
- Upload your video file with embedded subtitles
- Select subtitle track (if multiple languages exist)
- Choose output format (SRT, VTT, ASS)
- Click "Extract" to pull subtitles from video
- Download your standalone subtitle file
Processing Time: Extraction is instant (1-5 seconds). Burning subtitles takes 2-5 minutes per GB since the entire video must be re-encoded with overlay text rendering.
How Subtitle Processing Works
Two Types of Subtitle Integration
Soft Subtitles (Extractable)
Stored as separate data stream inside video container. Can be turned on/off by the player.
- Format: MKV, MP4, WebM containers
- Extraction: Instant (demux stream only)
- File size: Adds only 50-500 KB to video
- Editability: User can disable or switch languages
Hard Subtitles (Burned-in)
Permanently rendered onto video frames as pixel data. Cannot be removed or turned off.
- Format: Any video format (AVI, MP4, etc.)
- Creation: Requires full video re-encoding
- File size: Slightly larger due to text pixels
- Editability: Permanent; cannot be removed
Technical Processing Pipeline
Burning Subtitles (Adding to Video)
Extracting Subtitles (Removing from Video)
| Subtitle Format | Features | Compatibility | Best Use Case |
|---|---|---|---|
| SRT | Plain text only | Universal (99% players) | Standard subtitles |
| VTT | Supports styling, positioning | Web browsers, HTML5 video | Web embedding |
| ASS/SSA | Advanced styling, animations, fonts | VLC, MPC-HC, anime players | Styled subtitles, anime fansubs |
| SUB/IDX | Image-based (bitmap) | DVD players, VLC | DVD/Blu-ray subtitles |
Understanding Subtitle Quality and Performance
Subtitle Sync Accuracy Standards
Excellent Sync
- Timing: ±50ms from dialogue
- Viewer experience: Unnoticeable delay
- Quality: Professional standard
Acceptable Sync
- Timing: ±200ms from dialogue
- Viewer experience: Minor distraction
- Quality: Amateur/fan-made standard
Poor Sync
- Timing: >500ms off
- Viewer experience: Highly distracting
- Fix needed: Re-sync required
Processing Time Benchmarks
| Operation | 500MB Video | 2GB Video | CPU Usage |
|---|---|---|---|
| Extract subtitles | 1-3 seconds | 3-8 seconds | Low (10-20%) |
| Burn subtitles (simple SRT) | 60-150 seconds | 240-600 seconds | High (90-100%) |
| Burn subtitles (styled ASS) | 90-200 seconds | 360-800 seconds | Very High (95-100%) |
Why burning is slower: Every frame must be decoded, have text rendered on top, then re-encoded. A 10-minute 1080p30 video = 18,000 frames to process. Extraction just copies existing subtitle data without touching video frames.
File Size Impact Analysis
How Subtitles Affect Video File Size
- Soft subtitles (embedded): Add 50-500 KB regardless of video lengthA 2-hour movie subtitle file is typically 100-200 KB as plain text
- Hard subtitles (burned): Increase file size by 3-8%Text pixels add complexity to compression; more detail = larger encoded size
- Multiple soft subtitle tracks: ~100 KB per language trackA video with English + Spanish + French subtitles adds ~300 KB total
Pro Tips for Subtitle Management
1. Always Keep Soft Subtitles When Possible Instead of Burning
Many users burn subtitles unnecessarily. Soft subtitles (embedded as separate tracks) offer significant advantages: viewers can toggle them on/off, switch languages, customize appearance (size, color, position), and they don't require video re-encoding (preserving original quality).
When to burn: Only when the playback device doesn't support soft subtitles (older TVs, car displays, some social media platforms) or when you need guaranteed visibility for all viewers.
How to add soft subtitles: Use MKVToolNix (desktop) or mkvmerge to mux subtitle files into MKV containers without re-encoding. This takes 5-10 seconds vs. 5-10 minutes for burning.
2. Use VTT Instead of SRT for Web Videos to Enable Styling Control
SRT files support only plain text with no formatting. VTT (WebVTT) adds CSS-like styling, positioning controls, and metadata support. If embedding subtitles on websites via HTML5 <video> tag, VTT allows viewers to customize appearance in their browser settings.
Conversion: Converting SRT to VTT is instant and lossless. VTT also supports chapter markers and thumbnail previews (hovering over progress bar shows scene previews with text descriptions).
3. Extract Subtitles Before Editing Videos to Avoid Re-Sync Work
If you need to edit a video (trim, cut, rearrange scenes), extract soft subtitles first as a backup. Video editing shifts timestamps, breaking subtitle sync. With the original subtitle file, you can use subtitle editing tools (Subtitle Edit, Aegisub) to adjust timing mathematically rather than manually re-timing every line.
Time savings: Re-syncing a 2-hour movie manually takes 30-60 minutes. Using subtitle shift tools with the original file takes 30 seconds (calculate time offset, apply globally).
4. For Multi-Language Content, Embed All Subtitle Tracks in One File
Instead of creating separate video files for each language (English version, Spanish version, etc.), embed all subtitle tracks into a single MKV file. This reduces storage needs by 50-80% and simplifies file management. Players like VLC, Plex, and modern TVs let viewers switch languages on-the-fly.
Implementation: Use MKV container format (supports unlimited subtitle tracks). Tag each track with language metadata (eng, spa, fra) so players display "English," "Spanish," "French" in their menus.
5. Verify Subtitle Encoding (UTF-8) to Prevent Character Display Issues
Many subtitle files from the web use legacy encodings (Windows-1252, ISO-8859-1) that break non-English characters (é, ñ, ü, Chinese, Arabic). Always convert subtitle files to UTF-8 encoding before adding to videos. A single misencoded character can crash some players or display gibberish for the entire file.
Quick fix: Open subtitle file in Notepad++, VS Code, or Sublime Text. Select "Encoding → Convert to UTF-8" before uploading. This fixes 90% of character display problems (missing accents, question marks replacing text).
6. Use OCR Tools for Image-Based Subtitles (SUB/IDX from DVDs)
DVD/Blu-ray subtitles are bitmap images, not text. You cannot edit or extract them as text files directly. Use OCR (Optical Character Recognition) tools like SubtitleEdit with Tesseract to convert image subtitles to editable SRT/VTT format. Accuracy is 95-98% with manual cleanup needed.
Why this matters: Lets you translate, correct errors, or re-style DVD subtitles. Also enables searching subtitle content (find specific dialogue) which is impossible with image-based formats.
Subtitle Format Selection Guide
| Use Case | Recommended Format | Reasoning |
|---|---|---|
| General video playback (PC, TV, phone) | SRT (soft subtitle) | Universal compatibility, small file size, editable |
| Website embedding (HTML5 video) | VTT | Native web support, allows CSS styling, supports chapters |
| Social media upload (YouTube, Facebook, Instagram) | Burned-in subtitles | Platform auto-compression may strip soft subs; burned ensures visibility |
| Anime fansubs or styled content | ASS/SSA | Advanced styling, karaoke effects, multiple fonts/colors |
| DVD/Blu-ray authoring | SUB/IDX | Image-based format required by DVD specification |
| Accessibility (hearing impaired) | SRT or VTT with sound descriptions | Include [door slams], [music playing] annotations; both formats support this |
| Old devices (DVD players, car screens) | Burned-in subtitles | Legacy devices may not support any soft subtitle format |
Common Subtitle Problems & Solutions
Subtitles Out of Sync
Cause: Video framerate mismatch (23.976 fps vs 25 fps), or video was edited after subtitle creation.
Fix: Use subtitle editing tools (Subtitle Edit, Aegisub) to apply global time shift (+/- seconds) or framerate conversion. If subtitles drift progressively (sync at start, off by end), framerate mismatch is the issue.
Special Characters Display as � or ???
Cause: Subtitle file encoding is not UTF-8. Non-ASCII characters (é, ñ, ü, Chinese, Arabic) stored in wrong character set.
Fix: Open subtitle file in text editor, detect current encoding (often Windows-1252 or ISO-8859-1), convert to UTF-8, save. Use Notepad++, VS Code, or online converters.
Subtitles Don't Appear in Video Player
Cause: Subtitle track not embedded correctly, player doesn't support format, or subtitle track is disabled in player settings.
Fix: Verify subtitle file is in same folder as video with same filename (e.g., movie.mp4 + movie.srt). Check player subtitle settings to enable tracks. Try VLC which supports virtually all formats.
Extraction Says "No Subtitle Tracks Found"
Cause: Video has burned-in subtitles (part of video image) rather than soft subtitles (separate data stream). Cannot extract text from pixels.
Fix: Burned subtitles require OCR (optical character recognition) to extract. This is complex and error-prone. Prevention: always keep original subtitle files separate from video.
Subtitle Font Too Small or Wrong Position
For soft subtitles: Change settings in video player (VLC: Tools → Preferences → Subtitles/OSD). Adjust font size, color, position.
For burned subtitles: Cannot change after encoding. Must re-burn with different settings (larger font, different vertical position).
Privacy & Copyright Considerations
Browser-Based Processing Advantages
- Complete privacy: Videos and subtitles never upload to servers; all processing happens locally in browser memory
- No data retention: Files cleared from memory when browser tab closes; zero server-side logs
- Safe for confidential content: Suitable for corporate training videos, private family content, unreleased material
- Offline capability: After initial page load, works without internet connection
Copyright & Legal Notice
Subtitle files are derivative works and subject to copyright. Creating, distributing, or using subtitles for copyrighted content without permission may violate copyright law in many jurisdictions.
Legal uses include: Personal use with legally owned media, creating subtitles for your own original content, accessibility purposes (adding captions to home videos, educational material), fair use scenarios (commentary, criticism, education).
This tool is provided for legitimate subtitle management purposes. Users are responsible for ensuring compliance with copyright law in their jurisdiction.
Frequently Asked Questions
Basics & Getting Started
What's the difference between burning and embedding subtitles?
Embedding (soft subtitles): Subtitles stored as separate data track inside video container. Can be toggled on/off by viewer. No video quality loss. Extraction is instant. File size increase: ~100-200 KB.
Burning (hard subtitles): Subtitles permanently rendered onto video frames as pixels. Cannot be removed or disabled. Requires full video re-encoding (quality loss). File size increase: 3-8%.
Which should I choose: burn or embed?
Choose embedding when: Viewers may want to disable subtitles, multiple language support needed, preserving original video quality is important, or playback devices support soft subtitles (modern TVs, computers, phones).
Choose burning when: Target platform requires it (some social media auto-strips soft subs), playback device doesn't support soft subtitles (older DVD players, car displays), or you need guaranteed subtitle visibility for all viewers.
Can I add subtitles without re-encoding the video?
Yes, but only with soft subtitle embedding using desktop tools like MKVToolNix or ffmpeg. This process (called "muxing") copies video/audio streams unchanged while adding the subtitle track, taking 5-15 seconds with zero quality loss.
This browser tool burns subtitles (renders text onto video frames), which requires full re-encoding. For soft subtitle embedding without quality loss, use desktop software.
What subtitle formats can I upload?
Text-based formats (supported):
- SRT (SubRip): Most common, plain text with timestamps
- VTT (WebVTT): Web-optimized, supports styling and positioning
- ASS/SSA (Advanced SubStation): Styled subtitles with fonts, colors, effects
- SUB (MicroDVD): Frame-based timing format
Image-based formats (not supported for upload): SUB/IDX (DVD bitmap subtitles), PGS (Blu-ray). These require OCR conversion to text first.
How do I create a subtitle file if I don't have one?
You'll need subtitle creation/editing software:
- Manual creation: Subtitle Edit (free, Windows), Aegisub (free, cross-platform), Jubler (free, Java-based)
- Auto-generation (AI transcription): YouTube auto-captions (free but requires upload), Descript, Otter.ai, Whisper (OpenAI's free offline tool)
- Download existing: OpenSubtitles.org, Subscene.com (verify copyright compliance)
Burning Subtitles (Adding to Video)
How long does it take to burn subtitles onto a video?
| Video Length | File Size | Typical Time |
|---|---|---|
| 1 minute | ~100 MB | 10-30 seconds |
| 5 minutes | ~500 MB | 60-150 seconds |
| 10 minutes | ~1 GB | 2-5 minutes |
| 30 minutes | ~3 GB | 6-15 minutes |
Processing time depends on video resolution, framerate, and device CPU performance. 4K videos take 4x longer than 1080p at same duration.
Can I customize subtitle appearance (font, size, color, position)?
Yes. Before burning, you can adjust:
- Font family: Arial, Times New Roman, Helvetica, or custom fonts
- Font size: Typically 36-72pt for 1080p video (scales with resolution)
- Color & outline: Text color, outline/border color, shadow effects
- Position: Bottom, top, or custom vertical placement
- Background: Transparent, semi-transparent box, or solid background
Note: Once burned, these settings cannot be changed. Viewers cannot customize appearance like they can with soft subtitles.
Will burning subtitles reduce video quality?
Yes, slightly. Burning requires re-encoding the entire video. Quality loss depends on output settings:
- Minimal loss: Using high bitrate (8-12 Mbps for 1080p) produces near-identical quality to original
- Noticeable loss: Low bitrate (2-4 Mbps) shows compression artifacts, especially in detailed scenes
- Additional consideration: Subtitle text adds fine details (sharp edges, small letters) that compress poorly, slightly increasing file size
Best practice: Keep original video file as backup before burning. If quality is unacceptable, you can re-burn with higher settings.
Can I burn multiple subtitle tracks (e.g., English and Spanish) into one video?
No. Burning creates permanent text overlay. You cannot have two burned subtitle sets simultaneously without overlapping text.
Alternative solution: Embed both subtitle tracks as soft subtitles in MKV container using MKVToolNix. Viewers can then switch between English/Spanish in their player settings. This is the standard approach for multi-language video distribution.
What happens if subtitle timing is wrong before burning?
The incorrect timing becomes permanent once burned. Always verify subtitle sync by watching the video with soft subtitles first, then burn only after confirming perfect timing.
If you discover errors after burning: You must re-burn the video with corrected subtitle file. Cannot fix timing post-burn.
Extracting Subtitles (Removing from Video)
How can I tell if a video has extractable subtitles?
Method 1 - Check file format: Only MKV, MP4, and WebM containers commonly contain soft subtitle tracks. AVI rarely does.
Method 2 - Test in VLC: Open video in VLC → Subtitle menu. If you see "Track 1," "Track 2," etc., those are extractable soft subtitles. If menu says "Disable" only or is grayed out, subtitles are either burned-in or absent.
Method 3 - Use MediaInfo: Free tool (mediainfo.sourceforge.net) shows all tracks in a video file. Look for "Text" or "Subtitle" tracks in the output.
Can I extract burned-in subtitles from video?
Not easily. Burned subtitles are pixels, not text data. Extraction requires OCR (Optical Character Recognition) to read text from video frames—complex, error-prone, and time-consuming.
OCR software options: Subtitle Edit (free, with Tesseract OCR engine), SubtitleCreator, VideoSubFinder. Expect 90-95% accuracy requiring manual cleanup.
Better approach: Search for existing subtitle files online (OpenSubtitles.org, Subscene) rather than attempting OCR extraction.
Does extraction take a long time?
No. Extracting soft subtitles is instant (1-10 seconds) regardless of video length. The tool copies existing subtitle data without decoding video frames.
A 2-hour movie subtitle extraction completes in the same time as a 30-second clip extraction because file size/duration doesn't matter—only the subtitle data stream is processed.
My video has multiple subtitle tracks—can I extract a specific one?
Yes. The tool will list all available subtitle tracks with language labels (if properly tagged). You can select which track to extract:
- Track 1 (English): Primary language subtitles
- Track 2 (Spanish): Secondary language subtitles
- Track 3 (English SDH): Subtitles for hearing impaired with sound descriptions
You can extract all tracks individually or select specific ones needed.
What if extracted subtitles are in the wrong format?
You can convert between subtitle formats during extraction. The tool supports converting:
- ASS/SSA → SRT (removes styling, keeps text and timing)
- SRT → VTT (adds web compatibility)
- VTT → SRT (removes web-specific features)
- Any text format → Any other text format
Note: Converting styled formats (ASS) to plain formats (SRT) discards color, font, and position information permanently.
Why do extracted subtitles sometimes have wrong timestamps?
This happens when video was trimmed or edited after subtitle embedding. The subtitle timestamps reference the original video timeline, which no longer matches the edited version.
Fix: Use subtitle editing software to shift all timestamps by the offset amount. If first subtitle should appear at 00:00:05 but appears at 00:00:15, apply a -10 second shift to all lines.
Subtitle Formats & Compatibility
What's the difference between SRT and VTT formats?
SRT (SubRip Text):
- Plain text only, no formatting support
- Universal compatibility (99% of players)
- Simple timestamp format: HH:MM:SS,mmm
- Best for general use, offline video playback
VTT (WebVTT):
- Supports CSS-like styling, positioning, text formatting
- HTML5 video standard (native web support)
- Can include chapter markers, metadata
- Best for web embedding, allows user customization
Should I use ASS/SSA format for styled subtitles?
Use ASS/SSA when: You need advanced styling (multiple colors, fonts, effects), creating anime fansubs with karaoke effects, precise positioning requirements, or complex subtitle animations.
Avoid ASS/SSA when: Simple subtitles are sufficient (most use cases), targeting wide compatibility (many players don't support ASS styling), or file size is a concern (ASS files are larger than SRT).
Compatibility note: VLC, MPC-HC, and mpv fully support ASS. Mobile players and web browsers often ignore styling and treat ASS as plain text.
Can I use subtitle files across different video players?
Yes, if using SRT or VTT formats (universal compatibility). ASS/SSA styling may render differently or be ignored by some players.
Best practice for cross-platform use: Provide SRT as default format for maximum compatibility. Include styled ASS version as optional download for advanced users.
What are SUB and IDX files, and why can't I edit them?
SUB/IDX are image-based subtitle formats used by DVDs and older media. Each subtitle is a bitmap (picture of text) rather than editable text characters.
Why they exist: DVD specification predates modern text rendering. Image subtitles ensure identical appearance across all players regardless of font availability.
To edit SUB/IDX: Convert to SRT using OCR tools (Subtitle Edit with Tesseract). This "reads" the text from images (95-98% accurate) and creates editable text file.
How do I know which format my subtitle file is?
Check the file extension:
- .srt → SubRip text format
- .vtt → WebVTT format
- .ass or .ssa → Advanced SubStation format
- .sub → Usually MicroDVD or SUB/IDX (check for accompanying .idx file)
- .idx → DVD subtitle index file (pairs with .sub)
You can also open the file in Notepad/text editor. SRT/VTT/ASS are human-readable text; SUB/IDX contain binary data (unreadable characters).
Troubleshooting & Technical Issues
Why are my subtitles displaying with wrong characters (�, ???, gibberish)?
Cause: Character encoding mismatch. Subtitle file uses non-UTF-8 encoding (Windows-1252, ISO-8859-1, etc.) containing special characters that browser cannot interpret correctly.
Fix in 3 steps:
- Open subtitle file in text editor (Notepad++, VS Code, Sublime Text)
- Detect current encoding (editor usually auto-detects)
- Convert to UTF-8: File → Encoding → Convert to UTF-8, then save
This fixes 95% of character display issues (missing accents on é, ñ, ü; Chinese/Japanese/Arabic characters showing as boxes).
The tool says my subtitle file is invalid or corrupted—what's wrong?
Common causes:
- Wrong file format: Uploaded .txt file renamed to .srt without proper formatting
- Malformed timestamps: Incorrect format like 01:30:45 instead of 01:30:45,000
- Missing sequence numbers: SRT requires numbered entries (1, 2, 3...)
- Character encoding issues: File contains null bytes or control characters
Fix: Open subtitle file in Subtitle Edit software (free). It will auto-detect and fix most formatting errors. Re-save and try uploading again.
Subtitles are out of sync—how do I fix timing?
For constant offset (same amount off throughout): Use subtitle editing tools to apply global time shift. If subtitles are 2.5 seconds late everywhere, shift all lines by -2.5 seconds.
For progressive drift (sync at start, off by end): Framerate mismatch. Video is 25 fps but subtitles are timed for 23.976 fps (or vice versa). Use Subtitle Edit's "Change framerate" function to recalculate all timestamps.
Tools: Subtitle Edit (Windows), Aegisub (cross-platform), Jubler (Java-based), or online tools like subtitletools.com
Why does burning take so long compared to extraction?
Extraction: Copies existing subtitle data stream from video container (1-10 seconds). No video decoding needed.
Burning: Must decode every video frame, render text overlay, re-encode frames, and mux into new file. A 10-minute 1080p30 video = 18,000 frames to process individually.
This is why burning takes 2-5 minutes per GB while extraction is instant regardless of file size.
Can I process 4K videos with subtitles?
Extraction: Yes, no problem. Works instantly regardless of resolution.
Burning: Possible but very slow and may crash browser. 4K (3840×2160) has 4x more pixels than 1080p, requiring 4x more processing power. Browser memory limits may be exceeded.
Recommendations for 4K: Use desktop computer with 16+ GB RAM, keep videos under 1 minute, or downscale to 1080p before burning subtitles.
What browsers work best for subtitle processing?
- Chrome/Edge (Best): Fastest WebAssembly execution, best memory management for burning subtitles
- Firefox (Good): Works well, slightly slower subtitle burning than Chrome
- Safari (Fair): Adequate for extraction; burning may be slower on older versions
- Mobile browsers (Poor): Limited memory causes crashes with large videos; extraction only recommended
My subtitles extracted successfully but won't load in my video player—why?
Most common cause: Filename mismatch. For external subtitle files to auto-load, they must have identical filename to video (except extension).
✓ Correct:
- movie.mp4
- movie.srt
✗ Incorrect:
- movie.mp4
- movie_subtitles.srt or subtitle.srt
Other causes: Wrong encoding (convert to UTF-8), unsupported format (convert ASS to SRT), or subtitle track disabled in player settings.
Best Practices & Optimization
Should I keep original subtitle files after burning them into video?
Yes, always. Original subtitle files allow you to:
- Fix timing errors without re-transcribing entire video
- Translate to other languages (edit text, keep timestamps)
- Re-burn with different styling (font, color, position)
- Share subtitles separately for users who prefer soft subtitles
- Create multiple versions (full subtitles vs. SDH with sound descriptions)
Subtitle files are typically 50-200 KB each (negligible storage cost). Losing them means re-creating from scratch if changes are needed.
How can I make sure subtitles are readable on all devices?
Font size: Use 5-7% of video height. For 1080p (1920×1080), use 54-76pt font. Scales proportionally for other resolutions.
Color contrast: White text with black outline/shadow is most readable. Avoid yellow, cyan, or low-contrast colors.
Position: Bottom 10-15% of frame (above any video letterboxing). Never cover critical video content (faces, actions).
Font choice: Sans-serif fonts (Arial, Helvetica, Roboto) more readable than serif fonts, especially on small screens.
What's the best workflow for adding subtitles to multiple videos?
- Create/obtain subtitle files first: Transcribe or download all subtitle files before processing videos
- Verify sync on one sample video: Test subtitle timing on representative clip before batch processing
- Standardize naming: Ensure video and subtitle files have matching names for each pair
- Process in batches: Group similar videos (same format, resolution) for consistent output settings
- Quality check: Watch first 30 seconds and last 30 seconds of each output to verify proper burning
- Archive originals: Keep copies of original videos and subtitle files separately
How do I create subtitles for accessibility (hearing impaired)?
SDH (Subtitles for the Deaf and Hard of Hearing) requirements:
- Include sound descriptions: [door slams], [phone ringing], [suspenseful music]
- Speaker identification: Use "John:" or color coding when multiple people speak
- Non-verbal cues: [sighs], [laughs], [whispers]
- Music lyrics: ♪ Song lyrics here ♪ when singing is plot-relevant
- Off-screen dialogue: (voice off-screen) or italics for narration
Standards reference: Follow DCMP captioning guidelines or Netflix's subtitle style guide for professional-quality SDH.
Can I automate subtitle creation or do I need to type everything manually?
AI auto-transcription tools (recommended for long videos):
- Whisper (OpenAI): Free, offline, 95%+ accuracy for clear speech, supports 50+ languages
- YouTube auto-captions: Free, requires upload, 90-95% accuracy (needs manual cleanup)
- Descript, Otter.ai, Rev.com: Paid services with higher accuracy and automatic speaker labeling
Manual typing (better for short videos): Use Subtitle Edit or Aegisub. Play video, type subtitles, set timestamps with keyboard shortcuts. Takes 3-5x video length for experienced subtitlers.
Privacy, Security & Legal
Are my videos and subtitle files uploaded to your servers?
No. All processing happens in your browser using WebAssembly (client-side processing). Videos and subtitles load directly into browser memory without uploading to external servers.
Verification: You can disconnect internet after page loads and the tool still functions. This proves no server communication occurs during processing.
Is it safe to use this tool for confidential or copyrighted videos?
Privacy: Yes, completely safe. Browser-based processing ensures files never leave your device. Suitable for corporate training, unreleased content, personal videos, or any confidential material.
Copyright: User responsibility. Adding or extracting subtitles doesn't change copyright status of video. Ensure you have legal rights to modify the content.
Can I legally download subtitles from the internet and use them?
Subtitle files are derivative works subject to copyright. Legal status varies by jurisdiction:
Generally legal: Personal use with legally owned media (DVD/Blu-ray you purchased), creating subtitles for your own original content, fair use purposes (education, commentary, criticism).
Questionable/illegal: Distributing subtitles for copyrighted films without permission, commercial use of fan-created subtitles, using subtitles for pirated content.
Consult legal counsel for specific copyright questions. This tool is provided for legitimate subtitle management purposes only.
Does this tool work offline?
Yes, after initial page load. The WebAssembly FFmpeg library caches in your browser. You can disconnect internet and continue processing videos and subtitles. No network connection required for actual subtitle operations.
Technical Limitations & Disclaimer
This tool uses FFmpeg.wasm for client-side subtitle processing. Burning subtitles requires full video re-encoding with text overlay rendering via libass. Processing speed depends on device CPU performance, video resolution, and browser WebAssembly implementation.
Subtitle format support is limited to text-based formats (SRT, VTT, ASS, SSA). Image-based subtitles (SUB/IDX, PGS) require OCR conversion using external tools before upload. Extraction only works with soft subtitles (separate data streams); burned-in subtitles cannot be extracted without OCR.
Output video quality depends on encoding settings. Browser-based encoding may not match professional desktop software quality. For production workflows requiring perfect quality preservation or batch processing, use desktop tools (FFmpeg CLI, MKVToolNix, Handbrake).
Subtitle timing accuracy depends on source file quality. Users are responsible for verifying subtitle sync before distribution. This tool is provided as-is for general-purpose subtitle management.