Add Subtitles to Video Online
Upload a video and SRT/VTT subtitle file, then embed subtitles into the video in one click. Supports MKV and MP4 output.
Local processing protects your privacy
Video and subtitle files are never uploaded to any server. All processing is done locally in your browser, keeping your privacy fully protected.
Supports SRT and VTT
Compatible with the two most common subtitle formats: SRT (the standard format for subtitles downloaded online) and WebVTT (the web standard subtitle format).
Soft subtitles, no quality loss
Adds a separate subtitle track (soft subtitles). The video picture is completely unaffected, and subtitles can be toggled on or off during playback.
Drag and drop video files here
or
Supports MP4, WebM, MOV, MKV, AVI, and more
Use Cases for Adding Subtitles to Video
Learning & Education
- Add subtitles to foreign language learning videos to aid comprehension and support intensive listening practice.
- Merge online course videos with subtitle files into a single file for convenient offline study and archiving.
- Embed multilingual subtitles into teaching videos so one file can serve learners in different languages.
Content Creation & Publishing
- Add subtitles to vlogs or short videos to improve the viewing experience in silent environments (subway, library).
- Merge movie or TV show files with downloaded subtitle files for a more complete viewing experience.
- Add subtitles to corporate training videos to improve accessibility and meet content accessibility requirements.
How to Use
Upload Video
Click the upload area or drag and drop a video file. Supports MP4, MKV, WebM, MOV, and more.
Upload Subtitle File
Click to select a subtitle file. Supports .srt and .vtt formats.
Select Output Format
Select MKV (recommended) or MP4 output format.
Embed & Download
Click the "Embed Subtitles" button. Download the video once processing is complete.
About the Video Subtitle Adder
VideoKit's online subtitle adder is powered by WebCodecs technology — subtitles are embedded directly in your browser without any server upload. The tool muxes subtitles as a separate soft subtitle track without re-encoding the video, so processing is fast and quality is preserved.
Accepts SRT (the most common subtitle format, with precise timestamps) and VTT (the web standard subtitle format) as input. Output supports both MKV and MP4 containers, with MKV offering the most complete subtitle support — recommended as the first choice.
All file processing is done locally in your browser — video and subtitle data never leaves your device. Chrome or Edge is recommended for optimal performance.
Frequently Asked Questions
What is the difference between soft and hard subtitles?
Soft subtitles (also called external or muxed subtitle tracks) are embedded as a separate track inside the video file. They can be toggled on or off during playback without affecting video quality. Hard subtitles are burned directly into the video frames and cannot be turned off. This tool adds soft subtitles, which require a compatible player (VLC, system players, browsers, etc.).
Which subtitle formats are supported?
The two most common formats are supported: SRT (SubRip, .srt) and WebVTT (.vtt). SRT is the most widely used format — subtitles downloaded from the web are usually SRT. VTT is the web standard subtitle format used in HTML5 video. Both can be uploaded directly and the tool handles them automatically.
Which players can display subtitles in the output video?
MKV output subtitles can be displayed in VLC, PotPlayer, system players (macOS QuickTime, Windows Media Player), and browser video tags. MP4 output is also supported by most mainstream players. If subtitles do not display, VLC is recommended as it supports subtitles in virtually all formats.
Will my video files be uploaded to a server?
No. All video processing is done locally in your browser — files are never uploaded to any server. Your video and subtitle data stays entirely on your device.
Why is MKV the recommended output format?
MKV (Matroska) has the most complete support for WebVTT subtitles and is compatible with virtually all video and audio codecs, making it the most versatile choice. MP4 has broader playback compatibility but may not support direct muxing with certain codec combinations. When in doubt, choose MKV.
Which input video formats are supported?
Most common video formats are supported, including MP4, WebM, MOV, MKV, AVI, and more. Chrome or Edge is recommended for the best compatibility. If a format is unsupported, convert it to MP4 first using the format converter tool.