Generate Video Subtitles & Captions with AI (SRT, VTT) — Free in Your Browser

Why Every Video Needs Subtitles

Roughly 85% of social video is watched with the sound off, and that number keeps climbing. Subtitles are no longer a nice-to-have — they’re the difference between a viewer stopping to read your video and swiping past it. Beyond retention, captions are essential for:

Accessibility — making content usable for deaf and hard-of-hearing viewers
SEO — search engines index caption text, boosting video discoverability
International reach — subtitles are the fastest path to multilingual audiences
Compliance — many platforms and jurisdictions require captions for published content

The good news: you no longer need a transcription service, a freelancer, or expensive software. AI can generate studio-grade captions in a few minutes, in your browser, for free.

Subtitle File Formats: SRT vs VTT

Two formats dominate. Both are plain text; the difference is where they get used.

Format	Used By	Notes
SRT	YouTube, Premiere, Final Cut, DaVinci Resolve, Vimeo, most editors	The universal default. Simple structure, broad compatibility.
VTT (WebVTT)	HTML5 `<video>`, web players, streaming (HLS)	Web-native, supports styling and positioning.

If you’re not sure which to pick, go with SRT — you can always convert later.

Step-by-Step: Generating Captions with AI

1. Extract the audio track

Most transcription tools accept video files directly (MP4, MOV, WebM), but if yours doesn’t — or if you want to save time — extract the audio first. In most editors, File → Export → Audio Only gives you an MP3 or WAV in seconds. Keeping the audio file under 100 MB keeps browser-based tools snappy.

2. Run the file through a Whisper-based transcriber

Open an in-browser tool like Whisper STT. The first run downloads the Whisper model once (it’s cached locally after that). Pick the spoken language and upload your file.

Whisper is the same AI model used by many paid transcription services. It excels at:

Mixed speakers and interviews
Mild background music
Accented and non-native English
99+ languages

3. Export as SRT or VTT

When the transcript finishes, export directly to .srt (or .vtt). The file will already have timestamps aligned to your audio — no manual syncing.

4. Attach captions to your video

YouTube:

Open YouTube Studio → your video → Subtitles
Click Add language → pick language → Upload file → choose “With timing” → upload the SRT

Premiere / Final Cut / DaVinci Resolve: Drag the SRT straight onto your timeline. All three major editors import SRT natively and will render it as a burn-in or a sidecar caption track.

Social (Instagram, TikTok, X): Most platforms auto-generate captions, but their quality is inconsistent. Exporting a burned-in version from your editor using your own SRT gives you full control over wording, line breaks, and style.

Accuracy Tips

Even a very good AI transcription benefits from a final polish. The goal: under 5 minutes of cleanup per 10 minutes of video.

Fix proper nouns first. Names, brands, and product names are where AI misses most often. Do a find-and-replace.
Break long lines. Captions should rarely exceed 42 characters per line. Most editors let you batch-split long captions.
Adjust reading speed. Aim for 15–20 characters per second. If captions flash by too quickly, merge adjacent cues.
Match punctuation to delivery. If the speaker pauses, add a comma. If they finish a thought, end with a period. This is what separates pro captions from machine output.

Multilingual Subtitles

Want Spanish, French, or German subtitles on an English video? Two approaches:

Transcribe in the source language, then translate. Generate English SRT first, then paste into a translation tool and re-time if needed.
Use Whisper’s built-in translation. Whisper can translate audio from 99+ languages directly into English — useful for foreign-language source material.

Privacy Note for Unreleased Content

Uploading unreleased video to a cloud caption service creates an off-device copy. If you’re captioning unreleased trailers, brand work under NDA, or investigative journalism footage, browser-based AI keeps the asset local. Your video never touches a third-party server.

Getting Started

Skip the subtitle drudgery. Generate SRT and VTT captions in your browser with Whisper STT — free, private, and as accurate as any paid service.