Upload a video: supported formats

To dub a video in Dubly.AI you first need to add your source. There are two ways: a File Upload from your device, or a YouTube Link. This article walks through both, plus what file formats and limits apply.

Two ways to add a source video

Option 1: File Upload (from device)

Use this when your video is stored locally on your computer or a shared drive. Best for:

• Final masters not yet published online
• Highest-quality source files
• Confidential content you don’t want to host publicly How to:

1. From the Dashboard, click + Create Dub.
2. Choose the Upload Videofile tab.
3. Drag and drop your file, or click to browse.
4. Wait for the upload to finish.

Option 2: YouTube Link

Use this when your video is already on YouTube. Best for:

• Public content already published
• Slow upload speeds — our servers fetch the video directly
• Quick experiments and translations of existing web content How to:

1. From the Dashboard, click + Create Dub.
2. Choose the YouTube Link tab.
3. Paste a standard YouTube URL: https://www.youtube.com/watch?v=VIDEO_ID
4. Click Continue.

YouTube link format

• Supported: https://www.youtube.com/watch?v=VIDEO_ID
• Not supported: youtu.be short links and YouTube Shorts (/shorts/) If you have a Shorts URL, copy the video ID and paste it into the standard format:
• Original: https://www.youtube.com/shorts/UMLl2pnMJmQ
• Convert to: https://www.youtube.com/watch?v=UMLl2pnMJmQOther YouTube limitations:
• Private videos — Dubly can’t access them; you’ll see “Video not found”.
• Live streams in progress — wait for the stream to finish first.
• Playlist URLs — paste a single video URL, not a playlist.

Supported file formats

Item	Supported
File formats	MP4 and MOV only
Max file size	5 GB
Audio track	Required — at least one audio channel with spoken content
Channels	Mono or stereo
Duration	No hard cap on paid plans. Free trial dubs only the first 60 seconds.
Frame rate	Constant frame rate (CFR) recommended — variable frame rate (VFR) can cause timing issues during Lip-Sync
Codec / container	MP4 (H.264) works best. MOV is re-encoded internally.

Other formats (MKV, WebM, AVI, audio-only) are not accepted — the upload is rejected client-side with the message “Only mp4 and mov files are accepted”. Convert them to MP4 before uploading.

Audio-only input

Not currently supported. MP3, WAV, M4A files are rejected at upload — Dubly.AI is a video localization tool and the pipeline expects a video container. If you only have audio, wrap it into an MP4 with a black or static video track using a tool like FFmpeg or any common video editing tool before uploading.

What Dubly does with your file

The way your file is handled depends on the features you use. If you use Lip Syncing, Dubly re-encodes the video internally to normalize the frame rate and codec (H.264 MP4, up to 1920px width, capped at 30 FPS) to ensure stable processing. However, for standard audio dubbing, the original video resolution is maintained—if your input is 4K, the output remains 4K. In all cases, your original file is kept so you can re-download it later if needed.

Other sources (Google Drive, Dropbox, S3)

The create-dub modal in the web app offers only Upload Videofile and YouTube Link. You can’t paste a direct Google Drive or Dropbox link in the UI. If you need to pull videos from a CDN or cloud storage, use our public API (POST /api/v1/dubs/url) with a direct-download URL — for example, an S3 pre-signed URL or a ?dl=1-style direct link. See Batch Processing Multiple Videos for the API approach.

Still unsure?

If your file is on the edge — unusual codec, very large, embedded subtitles, low bitrate — convert it to a standard H.264 MP4 at 10–15 Mbps before uploading. That fixes most format-related issues in one step. If the upload still fails, see Fix a failed upload for the troubleshooting checklist.