Smallest AI's Lightning is a real-time text-to-speech API delivering ~100ms latency with expressive, human-like voices; in blind listening tests, listeners preferred it over OpenAI's GPT-4o-mini-TTS 76.2% of the time. OpenAI bundles TTS within its wider API; Lightning is purpose-built for low-latency voice agents and production applications.
Lightning Text-to-Speech
Hyper-realistic, expressive voices with ~100ms latency, built for real-time agents and long-form narration alike.
30+ Languages
Natural, human-like speech across 30+ languages, with voice cloning from just 5–15 seconds of audio.
Enterprise-Grade Compliance
SOC 2 Type II, GDPR, ISO 27001, and HIPAA-ready — with a Business Associate Agreement available for healthcare deployments.
Features
Benchmarks
Naturalness scores (higher is better) from listener evaluation. Source: Smallest AI Lightning v3.1 Pro model card.
Frequently
asked questions
Is Lightning more natural-sounding than OpenAI TTS?
Does OpenAI TTS support voice cloning?
Is OpenAI TTS good enough for real-time voice agents?
How does pricing compare?
What languages does Lightning support?
What does switching from OpenAI TTS to Lightning involve?