Simple, transparent pricing
The free tier is genuinely useful — word-level highlighting and BYOK support with no account. Pay only when you want managed premium voices.
- Word-level highlighting
- Smart text extraction
- Speed control
- Paragraph navigation
- BYOK — your own API key, any provider
- Managed voices
- Premium voices
- Priority support
- Everything in Free
- 500,000 managed characters per month
- Managed voices
- Premium voices
- Priority support
- Everything in Pro
- 2,000,000 managed characters per month
- Managed voices
- Premium voices
- Priority support
Custom licensing
Need a custom deployment, or commercial terms beyond the standard tiers? We offer flexible licensing for businesses of all sizes.
Contact UsBring Your Own Key (BYOK)
Already have API keys from a TTS provider? Use them with Proso for free on any tier — including the Free plan. Your keys are forwarded securely through our server for each request and never stored.
- OpenAI — High-quality voices with natural intonation
- ElevenLabs — Ultra-realistic AI voices with word timing
- Groq — Blazing-fast inference at low cost
- Cartesia — Low-latency streaming voices
Frequently Asked Questions
What happens when I run out of credits?
When your managed credits run out, managed voices pause until your next allocation. You can keep listening with your own API key (BYOK) on any tier — it never spends managed credits.
Can I use my own API keys?
Yes, on every tier — including Free — and it’s always free. Bring your own OpenAI, ElevenLabs, Groq, or Cartesia API key and use premium voices without spending any managed credits. Your keys are cached locally in your browser and securely forwarded through our server when you play audio. Keys are used for one request and immediately discarded — never logged or stored.
How do I install the extension?
Proso 1.2.10 is awaiting Mozilla Add-ons review. The listing link becomes installable when Mozilla publishes the approved version.
What's your refund policy?
Full refund within 7 days for annual plans, no questions asked. Monthly plans are prorated — you'll receive a refund for the unused portion of your billing period.
Do managed credits carry over?
No — unused managed credits do not carry into the next billing cycle. Your full allocation is available until the cycle ends.