Auto Caption Generator
Generate captions locally with Whisper Base in Hearably Pro, review the text and timing, then export SRT. Accuracy varies with speech, noise, language, and hardware.
Free: 3 audio uploads/day · 30-second preview · 120% boost · 3-band EQ
Captions are no longer optional. Every major social platform — YouTube, TikTok, Instagram, LinkedIn, Facebook — rewards captioned content with higher engagement, longer watch times, and broader reach. Studies consistently show that 80% of viewers are more likely to watch a video to completion when captions are available, and 85% of Facebook video is watched on mute. Whether you are a content creator, educator, marketer, or podcaster, adding accurate captions to your media is one of the highest-impact things you can do for your audience. The problem has always been the process: manual transcription is brutally time-consuming, and cloud-based auto caption services require you to upload your files to someone else's servers, wait in processing queues, and often pay per minute of audio.
Hearably Studio Pro runs the Whisper Base ONNX model locally through Transformers.js and the WebAssembly execution backend. The first use downloads roughly 150 MB of model data and caches it in the browser. Hearably does not upload the media file for transcription, but authentication, model downloads, and ordinary page analytics still use network requests. Organizations handling regulated or confidential material must assess their own policy and compliance requirements.
The transcription accuracy rivals cloud services like Otter.ai, Descript, and Rev's AI tier. Whisper was trained on 680,000 hours of multilingual audio data, giving it exceptional robustness against accents, background noise, overlapping speech, and domain-specific vocabulary. The model handles conversational speech, formal presentations, interviews with multiple speakers, and even music with lyrics. For content with technical jargon or proper nouns, you can review and correct the generated captions in the built-in editor before exporting — a workflow that takes a fraction of the time compared to transcribing from scratch.
Once captions are generated, you have full control over the output. The built-in caption editor lets you adjust timing, correct words, merge or split segments, and fine-tune the synchronization between text and audio. When you are satisfied, export as an SRT subtitle file — the universal format accepted by YouTube, Vimeo, Facebook, LinkedIn, and virtually every video editing application. The SRT file contains precisely timed text segments that video players overlay on your content, making it accessible to deaf and hard-of-hearing viewers, non-native speakers, and anyone watching in a sound-sensitive environment.
The caption generator, Magic Cut, 800% boost, and 10-band EQ are Hearably Pro features. The workflow runs in one browser tab, but every AI transcript and suggested cut must be reviewed before export. The free Studio tier is limited to 3 audio uploads per day, files up to 50 MB, a 30-second preview, 120% boost, and a 3-band EQ.
Need the same fix elsewhere? See also SRT Subtitle Generator, How to Add Captions to TikTok, Reels & Shorts and AI Podcast Editor Online — all three use the same audio engine, tuned per platform.
How Browser-Based AI Captioning Works — Whisper Base on ONNX WASM
Hearably Studio Pro loads onnx-community/whisper-base through @huggingface/transformers in a dedicated Web Worker. The current execution backend is ONNX Runtime WebAssembly. The roughly 150 MB model is downloaded on first use and can be reused from the browser cache.
The browser decodes the supported media, then OfflineAudioContext resamples the audio to 16 kHz mono. Whisper processes 30-second chunks with a 5-second stride and returns timestamped segments. The worker keeps inference off the main UI thread. Processing speed and accuracy vary by device, language, recording quality, and duration, so the transcript must be reviewed.
How to get the best audio on Auto Caption Generator
Use clean audio for the best transcription accuracy
Whisper handles background noise well, but cleaner audio produces more accurate captions with fewer corrections needed. Before captioning, consider using Hearably Studio's volume boost and EQ to enhance vocal clarity — boost the 2-4 kHz speech presence band and apply the high-pass filter to cut low-frequency rumble. Cleaner input means fewer manual corrections in the editor afterward.
Review and correct proper nouns after generation
AI speech recognition excels at common vocabulary but can struggle with brand names, technical terms, and uncommon proper nouns. After generating captions, use the built-in editor to search for and correct these terms. This targeted review is dramatically faster than full manual transcription — you are editing, not writing from scratch.
Adjust segment timing for natural reading speed
The auto-generated timing is based on speech boundaries detected by the model. Occasionally, segments may be too long or too short for comfortable reading. The caption editor lets you split long segments into shorter ones (aim for 2 lines, under 42 characters per line) and merge very short segments that flash by too quickly.
Export SRT for maximum platform compatibility
SRT (SubRip Text) is the most widely supported subtitle format across video platforms and editing software. YouTube, Vimeo, Facebook, LinkedIn, TikTok (via CapCut), Premiere Pro, Final Cut Pro, and DaVinci Resolve all accept SRT files natively. Always export as SRT unless a specific platform requires a different format.
Caption podcast episodes to create show notes and transcripts
The auto caption generator is not just for video. Drop a podcast MP3 or M4A file, generate captions, and export as SRT or copy the plain text. You now have a complete episode transcript for show notes, blog posts, and SEO. Many successful podcasters use AI transcription to repurpose every episode into written content.
Process long files in the background while you work
Transcription runs in a Web Worker thread, so the browser tab remains responsive during processing. Drop a 60-minute podcast or lecture recording and continue working in other tabs while the model processes. A progress indicator shows estimated time remaining. On modern hardware, even hour-long files complete in minutes.
Combine with Magic Cut for social media clips
After generating captions, use Magic Cut to remove silence and filler words. The captions automatically adjust their timing to match the shortened audio. Export the tight, captioned clip for TikTok, Reels, or YouTube Shorts — the combination of polished audio and accurate captions maximizes engagement on every platform.
Use captions to identify filler words before removing them
The generated transcript makes filler words like "um," "uh," "you know," and "like" visually obvious in text form. Review the captions to understand your filler word patterns, then use the filler word remover to automatically strip them. This workflow gives you both clean audio and clean text for repurposing.
Built for this exact use case
AI-Powered Transcription
OpenAI Whisper model runs locally via WebAssembly. Handles accents, background noise, multiple speakers, and technical vocabulary. No cloud processing — your audio stays on your device.
Built-In Caption Editor
Review, correct, and refine generated captions in a synchronized editor. Adjust timing, fix words, split or merge segments. See captions alongside the waveform for precise alignment.
SRT Subtitle Export
Export perfectly timed SRT files accepted by YouTube, Vimeo, TikTok, LinkedIn, and every major video editor. Universal subtitle format with segment timestamps and text.
Local Media Processing
The media file is decoded and transcribed locally rather than uploaded to Hearably. Model downloads, authentication, and page analytics still use network requests.
Choose your method
Different situations call for different tools. Hearably gives you both.
Chrome Extension
Enhance audio live while you stream. The extension intercepts your tab's audio and processes it in real-time — volume boost, EQ, presets — without downloading anything.
- Streaming on Auto Caption Generator, Netflix, Spotify
- Video calls on Zoom, Meet, Teams
- Supported browser tabs with audio
- When you want instant, always-on enhancement
Free Online Studio
Upload an audio or video file, apply volume boost + 10-band EQ, preview in real-time, then download the enhanced WAV. Your file never leaves your browser.
- Downloaded videos or music files
- Podcast episodes you want to boost before sharing
- Voice recordings, lectures, interviews
- When you need a permanently enhanced file
Pro tip: Use a YouTube-to-MP3 tool to download the audio, then enhance it in Hearably Studio with EQ + volume boost. Perfect for offline listening, DJ sets, or sharing on social media.
Three clicks to better audio
Install
Add Hearably from the Chrome Web Store or Microsoft Edge Add-ons.
Enhance
Click the Hearably icon and tap "Enhance." Boost kicks in instantly.
Enjoy
Adjust volume, EQ, and presets on supported browser tabs.
Frequently asked questions
How accurate is the auto caption generator?
Accuracy depends on language, audio quality, speaker clarity, accents, overlap, and background noise. Hearably has not published a controlled benchmark for this exact Whisper Base browser build. Treat generated captions as a draft and review all text and timestamps before publishing.
Do my files get uploaded to Hearably for captioning?
The media file is decoded and transcribed locally rather than uploaded to Hearably. The page still uses network requests for authentication, model downloads, and ordinary analytics; read the privacy policy for the full boundary.
What languages does the auto caption generator support?
Whisper was trained on multilingual data and supports over 90 languages including English, Spanish, French, German, Portuguese, Japanese, Chinese, Korean, Arabic, Hindi, and many more. Accuracy is highest for English and major European languages, but the model handles most widely spoken languages with practical accuracy for captioning purposes.
How long does it take to generate captions?
On modern hardware with a capable processor, the tool transcribes approximately 1 minute of audio in 3-5 seconds. A 10-minute video generates captions in under a minute. Longer files take proportionally more time but run in a background thread, so your browser remains responsive. GPU acceleration via WebGPU further reduces processing time when available.
Can I edit the generated captions before exporting?
Yes. The built-in caption editor displays all generated segments with their timestamps synchronized to the audio waveform. You can click any segment to play that portion of the audio, correct text errors, adjust start and end times, split long segments into shorter ones, and merge fragments. This edit-then-export workflow is how professional subtitlers work.
What subtitle formats can I export?
The primary export format is SRT (SubRip Text), which is the most universally accepted subtitle format across video platforms and editing software. SRT files contain numbered segments with timestamps and text, and are accepted by YouTube, Vimeo, Facebook, LinkedIn, TikTok (via CapCut), Premiere Pro, Final Cut Pro, DaVinci Resolve, and virtually every other tool that handles subtitles.
Does the auto caption generator work with video files?
Yes. Drop any video file — MP4, MOV, WebM, MKV — and the tool extracts the audio track automatically for transcription. The video itself is not re-encoded or modified. You receive captions timed to the original video, which you can then burn in or attach as a separate SRT track in your video editor.
Is the auto caption generator included in the free tier?
No. AI transcription, caption editing, and SRT export require Hearably Pro. The free tier provides 3 audio uploads per day, files up to 50 MB, a 30-second preview, 120% boost, and a 3-band EQ.
How is this different from YouTube's auto-captions?
YouTube generates captions only after you upload your video to their servers, and the results are tied to YouTube's platform. Hearably Studio generates captions locally before you upload anywhere, giving you a portable SRT file you can use on any platform. You also get a full editing interface to correct errors before publishing — YouTube's editor is more limited and corrections are not portable.
Can I use this for meeting recordings and lectures?
Absolutely. The auto caption generator handles any spoken audio — podcasts, lectures, meetings, webinars, interviews, and presentations. For multi-speaker recordings, the model detects natural speech boundaries and creates appropriately segmented captions. The resulting transcript doubles as searchable meeting notes or lecture documentation.