Pick AssemblyAI if
voice-product engineers who will pick Universal-3.5 Pro vs Universal-2 and close the socket.
Read the AssemblyAI pageAssemblyAI vs Soniox
Our take
Pick AssemblyAI if voice-product engineers who will pick Universal-3.5 Pro vs Universal-2 and close the socket. Pick Soniox if voice teams who will start on the API hour rates ($0.10 async / $0.12 realtime) and only open the App when they want a weekly-credit scribe at $0. Skip AssemblyAI if people who want a local MIT model (OpenAI Whisper) with no vendor invoice.
AssemblyAI
Voice AI API (pre-recorded STT
Best for
AssemblyAI Hours of audio billed on a rate card
Soniox Realtime speech you meter in hours or tokens
Free plan
AssemblyAI $0 · $50, no credit card. Free-tier streaming concurrency 5 new streams/min vs PAYG 100
Soniox $0 · /month. Smart Scribe, Translator, Voice Typing. Weekly free credits. Mobile / desktop / web. Online or offline record
Lowest paid
AssemblyAI Universal-2 (pre-recorded) $0.15
Soniox STT text tokens $3.50
Next step up
AssemblyAI Universal-3.5 Pro (pre-recorded) $0.21
Soniox Pro $19.99/mo
Coding agent
AssemblyAI Voice Agent API
Soniox
Watch out
AssemblyAI Streaming bills idle socket time
Soniox New API keys have no free credit pack
Last checked
AssemblyAI 2026-10-20 · assemblyai.com/pricing
Soniox 2026-10-22 · soniox.com/pricing
Which one, then?
Pick Soniox if
voice teams who will start on the API hour rates ($0.10 async / $0.12 realtime) and only open the App when they want a weekly-credit scribe at $0.
Read the Soniox page