Captionwright – AI Video Captions, Subtitles & Transcripts

Automatic captions for your WordPress videos – free, private and without per-minute fees.

Captions are required for pre-recorded video under WCAG 2.1 (success criterion 1.2.2) – the standard behind the US ADA Title II rule for state and local governments, the European Accessibility Act and the EU Web Accessibility Directive for public bodies. Writing captions by hand is slow, and captioning services charge per minute – often $0.25 a minute for AI captions and $1.99 a minute for human captions.

Captionwright writes them for you, right inside WordPress:

1. Go to Media → Captions and click Generate next to a video or audio file.
2. OpenAI’s Whisper speech model listens to the file inside your browser tab (WebGPU when your computer has a graphics card, WebAssembly otherwise).
3. Check and edit the text next to a live preview, then save.

Your videos immediately show the captions in the core Video block and in [video] shortcodes – no theme changes needed. A clickable transcript below the video lets visitors – and search engines – read every word.

Who it is for

• Schools, universities and public bodies that must caption their recorded video
• Course creators and membership sites that want captions and searchable transcripts
• Podcasters who want a transcript under every episode
• Agencies that need to make client sites accessible without a per-minute bill
• Churches, clubs and nonprofits that publish recordings of talks and meetings

Features

• Automatic captions in 30 languages, or an English translation of any of them
• Runs locally in the browser: no uploads, no account, no API key, no usage fees
• Edit captions next to a live preview before saving
• Captions are added automatically to the core Video block and the [video] shortcode
• Transcript block with clickable times that jump the player, and the current sentence highlighted while it plays
• Optional transcript below every captioned video, which also helps search engines and AI assistants read your videos
• [captionwright_transcript id="123"] shortcode for classic editors and page builders
• Standard WebVTT subtitle files you can download and reuse anywhere
• Four model sizes, from Tiny (38 MB) to Large v3 Turbo (best accuracy, needs a graphics card)

Captionwright Pro

For larger sites, Captionwright Pro adds:

• Caption the whole Media Library with one click – pause and resume any time
• Translate captions into 30 languages with timings kept in sync
• Interactive transcripts for YouTube and Vimeo embeds
• Cloud mode with your own Groq or OpenAI key for large libraries

Everything in the free plugin stays free, with no limits on the number of videos or minutes.

Privacy

Speech recognition happens on the computer of the person who clicks Generate. The audio is decoded in the browser and is never sent to any server. Captions are saved as WebVTT files in your own uploads folder.

External services

This plugin downloads the Whisper speech-recognition model files from Hugging Face (huggingface.co) the first time you generate captions in a browser, and from the browser cache afterwards.

• What is sent: ordinary HTTP requests for the public model files (for example onnx-community/whisper-base), which include your IP address and browser user agent as with any web request. No audio, text or site data is sent.
• When: only after an administrator turns on “Allow model download” under Media → Captions → Settings, and only when someone clicks Generate.
• Hugging Face terms of service: https://huggingface.co/terms-of-service
• Hugging Face privacy policy: https://huggingface.co/privacy

Third-party libraries

• Transformers.js 4.3.1 by Hugging Face – Apache License 2.0 – https://github.com/huggingface/transformers.js
• ONNX Runtime Web 1.31.0-dev.20260914-8d85527a0 by Microsoft – MIT License – https://github.com/microsoft/onnxruntime
• Whisper model weights by OpenAI (ONNX conversions by the onnx-community organisation) – MIT License – https://github.com/openai/whisper

The library files ship unmodified in vendor/transformers/ together with their licence texts. They are copied byte for byte from the published npm packages:

• transformers.min.js – dist/transformers.min.js from @huggingface/transformers 4.3.1. Source code: https://github.com/huggingface/transformers.js/tree/4.3.1
• ort-wasm-simd-threaded.asyncify.mjs and ort-wasm-simd-threaded.asyncify.wasm – from dist/ in onnxruntime-web 1.31.0-dev.20260914-8d85527a0. Source code: https://github.com/microsoft/onnxruntime/tree/8d85527a010e294a26b274749f74294b2a32cec5

The .wasm file is ONNX Runtime compiled to WebAssembly. It is the engine that runs the Whisper model in the browser, on the graphics card (WebGPU) as well as on the processor, so captions cannot be generated without it. Only this one runtime file is included, not the other ONNX Runtime variants.