Browser caption generator

Free Auto Caption Generator that keeps your video private

No uploadNo signupBurn-in or SRT/VTTMultilingual

This tool generates captions for any video, entirely in your browser tab. The file you drop on the page stays on your device. Speech recognition runs locally against a Whisper model, captions render in a live preview, and the final output, whether burned into the MP4 or exported as an SRT or VTT file, comes off your own machine. No upload, no transcoding queue, no account to make.

Drop your video or audio file here

or click to browse

Supports video and audio files up to 2048MB

Why captions in the browser

It works the way you would expect. Pick a styling preset or build your own (font, color, size, position, background pill, karaoke highlight), edit the auto-generated transcript inline to fix any words Whisper got wrong, then export. The default is a hardcoded burn-in, where the captions are baked into the video frames so they show up everywhere, but the SRT and VTT exports are right there for anyone who needs a separate sidecar file.

Why bother running this in the browser when every other caption generator uploads to a server. Three reasons. Privacy-sensitive material (medical clips, legal recordings, anything under NDA) should not be sitting on a third-party server, even briefly. Free tiers on the upload-based competitors come with watermarks, 10-minute caps, or a signup gate. And running locally means there is no rate limit and no queue: a 30-minute lecture takes as long as your laptop needs, not as long as someone else's server queue.

When this tool fits

TikTok and Reels

Burn captions directly into 9:16 video so they show up even when viewers watch with sound off. The preview honors the bottom-center safe zone the platforms use for their own UI.

YouTube videos and Shorts

Export an SRT to upload alongside your video for closed captions, or burn them in for Shorts where the platform deprioritizes opt-in captions.

Podcasts and audio

Drop an MP3 or WAV file directly. Whisper transcribes the audio, and you can export the transcript as SRT, VTT, or use the inline editor as a fast cleanup pass.

Course content and tutorials

Auto-generated captions help comprehension and watch time. Edit the transcript inline to fix technical terms and acronyms Whisper does not recognize.

Accessibility (a11y)

Closed captions are part of WCAG 2.1 compliance for video content. Generate them in seconds, then refine the timing and speaker labels in the inline editor.

Multilingual content

Whisper handles 99 languages. The same workflow applies whether the source audio is English, Spanish, Hindi, Mandarin, or anything else.

How to add captions to a video

1 Drop your video

Click or drag a video or audio file onto the upload box. The file is read into the browser tab and never uploaded anywhere.

2 Generate the transcript

Whisper transcribes the speech locally, with progress shown in real time. Edit any words it got wrong right inside the transcript panel.

3 Style your captions

Pick a preset or customize font, color, size, background pill, and position. The live preview overlay shows exactly what the burn-in will look like.

4 Export

Download an SRT or VTT sidecar file, or burn the captions into the video and download an MP4 with the captions baked in.

Frequently asked questions

Is my video uploaded anywhere?

No. The file you drop on the page is read by the browser tab and stays there. Speech recognition runs locally against a Whisper model that downloads once and caches in your browser. You can verify this in DevTools by watching the Network tab while you generate captions.

How accurate are the captions?

Accuracy depends on audio quality and the language. Clean English speech typically lands around 95 to 97 percent. Heavily accented speech, technical jargon, or low-quality audio drops the accuracy. The transcript editor is built for fixing these cases quickly.

What languages are supported?

The underlying Whisper model handles 99 languages. The model auto-detects the language from the audio, so you do not have to pick one ahead of time.

SRT vs VTT, which should I use?

Use SRT for almost everything: YouTube, Facebook, Vimeo, most video players, Premiere, Final Cut. Use VTT when you are embedding captions on a website with an HTML5 video player, since the WebVTT spec supports styling cues that SRT does not.

Can I burn the captions into the video itself?

Yes. The default export option burns the captions directly into the MP4 video frames, which means they show up on every platform and every device, even ones that do not support closed captions.

Is there a free limit on how long the video can be?

No length cap on the captioning itself, but very long videos depend on your device having enough memory to hold the audio and run Whisper. On laptops you can comfortably handle hour-long content. On phones, stick to clips shorter than five minutes for burn-in.

Will there be a watermark on the exported video?

No. The burn-in export contains only your video and the captions you styled. No VidStudio logo, no watermark, no signup wall in front of the download.

Does it work on mobile?

It opens and runs on mobile, and you can transcribe short clips. The burn-in step is heavy on memory and slow on phones, so for anything longer than five minutes the page shows a warning recommending desktop for the burn or downloading the SRT instead.

More caption tools

Same browser-local engine, tuned for specific destinations and workflows. Pick the one closest to the job you are doing.

By platform

Captions for TikTok

Add captions to TikTok videos in your browser. Auto-generate, edit, style with the 9:16 safe zone honored, then download a burned-in MP4. Free, no app required.

Captions for Instagram Reels

Add burned-in captions to Instagram Reels in your browser. Reels-specific safe zone preset, free, no Meta upload, no watermark, no signup.

Captions for YouTube Shorts

Add captions to YouTube Shorts in your browser. Burn into the MP4 for the Shorts surface, or export SRT for the longform CC button. Free, no upload, no signup.

Podcast Captions and Transcripts

Generate full transcripts and SRT or VTT captions for podcast episodes in your browser. Free, no upload, multilingual, ready for episode page SEO and accessibility.

By feature

Auto Captions, No Upload

Generate captions without uploading your video. Whisper and FFmpeg run as WebAssembly inside the browser tab. Verifiable in the Network panel in under a minute.

Auto Captions, No Signup

Generate captions without creating an account. No email, no Google sign-in, no Stripe wall. Drop a video, get captions, leave. Free, runs in your browser.

Free Captions, No Watermark

Burn captions into video with no VidStudio watermark on the export. Free tier is the full feature set: no logo, no signup, no upload, no metadata tag.

SRT Generator

Turn any video or audio file into a clean SRT subtitle file in your browser. Standard SubRip format with millisecond timecodes. Free, no upload, no signup.

VTT Generator

Generate WebVTT subtitle files in your browser. Standard WEBVTT header, millisecond cue timing, ready for HTML5 video track elements. Free, no upload, no signup.

By output type

Add Subtitles to Video

Add subtitles to any video in your browser. Auto-generate from the audio with Whisper, edit inline, then burn into the MP4 or export SRT or VTT. Free, no upload.

Burn Subtitles into Video

Burn subtitles directly into video frames so they show up on every platform and every device. Browser-local processing, no upload, no watermark, free.

Closed Captions Generator

Generate closed captions for video with non-speech audio cues and speaker labels. WCAG 2.1 oriented, browser-local processing, free, exports SRT and VTT.