Video and audio formats that work in your browser
A filename such as MP4 or WebM describes a container. The audio and video inside use codecs, and your browser must understand those codecs before CaptionKite can hear the file.
Formats that usually work best
CaptionKite accepts these common video and audio files plus other formats your browser can decode. Chrome or Edge is the best first choice when compatibility matters.
Why the extension does not tell the whole story
Two files can both end in .mp4 while using different internal audio codecs. One may open immediately and the other may fail. This does not necessarily mean the file is damaged; the browser may simply lack a decoder for that combination.
If a file plays in a desktop app but not in the browser, convert a copy to a common MP4 or extract its audio as WAV, M4A, or MP3. Transcribing audio alone is often faster and uses less memory.
Local file and direct URL limits
Local files are read incrementally, so a high-resolution video does not need to fit entirely in memory. Transcription memory still grows with audio duration. The smaller direct-URL ceiling limits browser download failures and protects visitors from unexpectedly fetching very large remote files.
A web page URL is not always a media URL
A direct URL points to the video or audio file itself and allows your browser to fetch it. A normal YouTube watch page, a sign-in screen, or a protected streaming page does not. Authorized Vimeo or Zoom download links can work when they resolve to accessible media and permit cross-origin browser access.
CaptionKite does not bypass passwords, permissions, disabled downloads, or a provider's access controls. Protected playback will be handled by the planned browser extension only after the user opens and plays content they are allowed to view.
If your file will not load
- Try the latest Chrome or Edge.
- Confirm the file plays normally on your computer.
- Use a local file instead of a remote link.
- Convert a copy to MP4, MP3, WAV, or M4A.
- For a long video, extract or split the audio into shorter sections.
- Read the complete transcription troubleshooting guide.