Listen to the web.
Your way.
A free, open-source Firefox extension that reads any webpage aloud with premium AI voices and real-time word-level highlighting.
The Future of Web Reading
Technology has transformed how we consume information. With advances in artificial intelligence and text-to-speech, listening to the web feels natural.
Install Proso for Firefox
Proso is published on Mozilla Add-ons. Firefox 109 or later is required.
Before listening, configure a provider API key, a synthesis host you operate, or an eligible managed plan. Provider charges may apply.
Everything you need to listen to the web
Premium voices, real-time highlighting, and total privacy — no compromises.
Premium AI Voices
Choose from OpenAI, ElevenLabs, Groq, or Cartesia. Bring your own API key or use managed credits.
Word-Level Highlighting
Follow along as Proso highlights each word in real-time. Never lose your place, even on long articles.
Smart Text Extraction
Automatically detects article content, strips ads and navigation clutter. Or select exactly what you want to hear.
Privacy by Design
API keys cached locally in your browser, forwarded securely for synthesis and never stored on our servers. The public AMO build sends no usage telemetry. The text you ask to hear is sent to your configured synthesis destination. See our privacy policy for details.
Up and running in seconds
Three steps to transform any webpage into an audio experience.
Install the Extension
One click from Mozilla Add-ons installs the signed build. No account needed, no signup forms. To hear audio on the free tier, add your own provider API key in settings or point Proso at a synthesis host you run yourself — both are free on every tier.
Navigate to Any Page
Open any article, blog post, documentation, or webpage. Click the Proso icon in your toolbar.
Listen
Text is read aloud with word-level highlighting. Control speed, skip paragraphs, and follow along visually.
Simple, transparent pricing
The free tier is genuinely useful — not a crippled trial. Pay only if you want premium voices.
- Word-level highlighting
- Smart text extraction
- Speed control
- Paragraph navigation
- BYOK — your own key from a supported provider
- One subscription for Proso and Lectrice
- Managed voices
- Premium voices
- Priority support
- Everything in Free
- One subscription for Proso and Lectrice
- 500,000 managed credits per month
- Managed voices
- Premium voices
- Priority support
- Everything in Pro
- One subscription for Proso and Lectrice
- 2,000,000 managed credits per month
- Managed voices
- Premium voices
- Priority support
Bring Your Own Key (BYOK)
Already have an OpenAI, ElevenLabs, Groq, or Cartesia API key? Use supported premium voices with BYOK on any tier, including Free. Proso charges no BYOK subscription fee; provider usage is billed separately. No managed credits are spent.
How Proso compares
An honest look at how we stack up against the alternatives.
| Feature | Proso | Speechify | NaturalReader |
|---|---|---|---|
| Free tier | Free forever, BYOK included | Limited | Limited |
| BYOK support | ✓ All tiers | ✗ No | ✗ No |
| Open source | ✓ AGPL-3.0 | ✗ No | ✗ No |
| Word-level sync | ✓ Free | Limited on free tier | Available (paywall unclear) |
| Starting price | $0 | $139/yr | $119/yr |
| Privacy | ✓ No data collection | Cloud processing | Cloud processing |
| Firefox support | ✓ First-class extension | Web app only | Web app only |
Built in the open
Proso is free and open-source software licensed under AGPL-3.0. The entire codebase is auditable, and contributions are welcome.
Need a commercial license? Proso offers dual licensing for businesses that need terms beyond AGPL-3.0.
Commercial Licensing