Async

Async Developer Platform is a low-latency text-to-speech (TTS) API for developers, businesses, and creators building real-time voice apps, conversational agents, and voice-driven workflows.

Key capabilities include:

• Real-time TTS with human-like prosody, tuned for natural intonation, pronunciation, and emotional inflections, with a reported 166 ms median time-to-first-byte (TTFB) for fast turn-taking.
• Voice cloning from a short sample, plus access to a premium catalogue of 500+ voices.
• Multilingual speech generation with support for 15+ languages through the same API.
• Integrations for common voice stacks and automation, including Pipecat, LiveKit, and n8n (plus Twilio support in docs).

Pricing: Freemium with 10 minutes free, then pay-as-you-go from $0.50/hour; unlimited voice cloning is included within the pay-as-you-go plan.

Notable for combining low-latency performance, enterprise reliability (24/7 SLA support, 99.9% uptime SLA, SOC 2 compliant infrastructure), and cost positioning against alternatives such as ElevenLabs and Cartesia, while offering a large voice catalogue and cloning options aimed at production voice applications.