Auto Caption Video Editor
Add AI auto-captions to your videos free. Whisper AI runs locally in your browser. Choose from 45+ styles, edit text, and export MP4. No watermark, no upload.
- Whisper AI
- 45+ Styles
- No Watermark
- 100% Private
100% secure. Your video never leaves your device.
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How do I add auto-captions to a video for free?
Upload your video, click "Generate Captions," and let Whisper AI transcribe the audio. Choose a style from 45+ options (Neon, Gradient, Comic), fix any typos in the text tab, and hit Render to download your captioned MP4.
- Price
- 100% Free, no credits
- Account required
- No
- Video uploaded
- No, runs locally
- Watermark
- None
- AI Model
- Whisper Tiny (English)
- Caption styles
- 45+ pre-designed styles
- Output format
- MP4 (H.264) + AAC audio
- Best for
- TikTok, Reels, YouTube Shorts
- Max resolution
- 1080p Full HD
- Works on
- Chrome, Edge, Firefox (Desktop)
How to add captions in 3 steps
- 1
Upload your video
Choose an MP4, WebM, or MOV. The video opens locally in your browser.
- 2
Generate AI captions
Click "Generate Captions". Whisper AI will listen to the audio and transcribe it in seconds.
- 3
Style, edit, and export
Choose a style, fix any typos, and click Render to download your captioned MP4.
Auto Caption FAQ
Quick answers about accuracy, privacy, and styling.
How does the AI auto-caption generator work?
We use OpenAI Whisper, a state-of-the-art speech recognition model. It runs entirely in your browser using WebAssembly. It listens to your video audio and generates perfectly timed text.
Is this auto caption editor free?
Yes, it is 100% free. There are no watermarks, no hidden fees, and no sign-ups required.
Do I need to upload my video to a server?
No. The entire process (audio extraction, AI transcription, and video rendering) runs locally in your browser.
Are the captions 100% accurate?
Whisper is highly accurate for clear English, but background noise or strong accents can cause errors. Use the "Edit text" tab to fix mistakes before rendering.
Can I change the caption style?
Yes. We offer 45+ styles including Neon, Gradient, Vaporwave, Comic, and Classic. You can also change the text color, size, and position.
Can I edit the captions?
Yes. Click the "Edit text" tab in the left sidebar. You can rewrite any line of text. The preview updates instantly.
Does it keep the original audio?
Yes. The original audio is trimmed to match your clip and exported in the final MP4.
What video formats are supported?
MP4, WebM, MOV, and MKV. We recommend MP4 (H.264) for the fastest rendering.
What resolution is the output?
The default output is 1080x1920 (Full HD). We also support 1:1 and 4:5.
Does it work on mobile phones?
It runs in mobile browsers, but desktop is highly recommended. Rendering a video and running the AI model uses a lot of memory.
What is the max file size?
We recommend files under 1GB. Browsers have memory limits, and large files may crash the tab.
Why does rendering take a while?
Because everything happens on your device. It has to run the AI model, draw the captions on a canvas, and re-encode the video using your local CPU/GPU.
Can I use this for YouTube Shorts?
Yes. The 9:16 format is perfect for Shorts. The 60-second trim preset is ideal.
Can I use this for Instagram Reels?
Yes. The exported MP4 is ready for Instagram. The 9:16 and 4:5 formats are supported.
Do I need to install CapCut or Submagic?
No. This is a completely free, browser-based alternative to Submagic and CapCut for adding auto-captions.
What if my video is already vertical?
You can still use this tool to add auto-captions and stylish text overlays to it.
Does the AI recognize multiple speakers?
It will transcribe everything that is said, but it does not differentiate between speakers (e.g. Speaker 1 vs Speaker 2).
Can I remove the captions?
Yes. If you do not generate captions, the video will render without them.
Why does the AI hallucinate text?
Whisper sometimes generates text during long silences or heavy background noise. You can easily delete these lines in the "Edit text" tab.
Do I need to pay for Whisper?
No. The model runs locally in your browser, so there are no API costs. It is completely free.
When auto-captions work best
Whisper AI is incredible, but it is not magic. Here is how it handles different types of audio.
| Audio Type | Result | Notes |
|---|---|---|
| Clear English speech (Talking head) | Perfect | Whisper AI is incredibly accurate with clear, direct speech. Expect 95%+ accuracy. |
| Background music / Noise | Works, with caveats | Heavy background noise can confuse the AI. It may skip words or hallucinate text. Edit the text tab to fix. |
| Multiple speakers (Podcasts) | Works, with caveats | It will transcribe all speakers, but it will not label who is speaking (Speaker 1, Speaker 2). |
| Strong accents / Mumbling | Poor | Whisper-tiny is optimized for English, but heavy accents may result in incorrect words. |
| Non-English languages | Poor | This specific tool uses the English-only Whisper model for maximum speed and accuracy. |
| Singing / Rap | Poor | ASR models struggle with singing. You will need to type lyrics manually. |
Tips for perfect captions
Check for hallucinations
Whisper AI sometimes invents words during silence. Read through the caption lines and delete any empty or hallucinated text.
Use the Edit Text tab
If a name or brand is spelled wrong, click the "Edit text" tab on the left and correct it before rendering.
Keep captions safe from UI
On TikTok and Reels, the bottom right corner has buttons. Drag your captions to the middle or top to avoid them.
Test the timing
Hit "Play" in the preview to make sure the captions appear in sync with the audio.
ToolDeck vs Submagic & CapCut
Submagic and CapCut charge monthly fees, add watermarks, and upload your videos to their servers. ToolDeck is entirely local and free.
| Feature | TToolDeck | Submagic / CapCut |
|---|---|---|
| Uploads video to a server | No | Yes |
| Adds a watermark to export | No | Yes |
| Requires monthly subscription | No | Yes |
| Has manual text editing | Yes | Yes |
| Offers 45+ caption styles | Yes | Yes |
| Works in your browser | Yes | Yes |
| No daily export limits | Yes | No |
What you get for free
Whisper AI Local Processing
Powered by OpenAI Whisper running via WebAssembly. Your audio is never uploaded to a server.
45+ Caption Styles
Neon, Glitch, Vaporwave, Comic, Gradient. Instantly apply viral caption styles to your video.
Inline Text Editor
AI makes mistakes. Fix typos directly in the editor before rendering. Changes appear instantly.
Drag & Drop Positioning
Move the captions anywhere on the screen. Perfect for avoiding UI elements on TikTok and Reels.
No Watermark
Export a clean 1080p MP4 file. We never stamp our logo on your content.
Original Audio Kept
The original audio track is copied untouched. Your music and voiceover remain intact.
100% Private Video Processing
There is no upload step and no account. The Whisper AI model runs inside your browser using WebAssembly. Your video and audio are never sent to a server. Read how we keep it private.
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