Speechmatics vs AssemblyAI: Which Speech-to-Text API Delivers?

Teams switching from AssemblyAI often choose Speechmatics for speaker diarization included at no extra charge, 55+ languages in real time, and on-premises, on-device and air-gapped deployment. For other options, see how Speechmatics compares with Deepgram, Google, Microsoft Azure and OpenAI.

Yes. Speechmatics consistently outperforms AssemblyAI in real-world transcription accuracy. On G2, Speechmatics scores 90% for accuracy in noisy settings versus AssemblyAI's 80%, and 94% for environmental noise adaptation versus 83%. Our Ursa 2 model is trained on over one million hours of diverse audio data, built for accuracy across accents, dialects, and challenging audio environments.

Here are recent benchmarks from Daily (Pipecat), where Speechmatics were recognized as a top-tier provider for real-time voice agents, sitting firmly on the "Pareto frontier" — and see how Speechmatics integrates with Pipecat.

Speechmatics supports 55+ languages with a single model covering all accents and dialects. AssemblyAI lists up to 99 languages for pre-recorded audio, while its most accurate real-time model, Universal-3.6 Pro Realtime, supports 32. Speechmatics has production-grade multilingual support across all deployment modes — scoring 91% versus AssemblyAI’s 78% for multilingual voice recognition on G2. Our new Melia model also adds native code-switching across all 55+ supported languages in a single pass.

Yes. Speechmatics offers real-time speaker diarization at no extra charge. AssemblyAI bills speaker diarization as a paid add-on ($0.12/hr in streaming, $0.02/hr in batch) and charges multichannel audio per channel. For use cases like live meeting transcription, call centers, and voice agents, real-time speaker identification is critical.

Yes. Speechmatics offers mature, production-ready on-premises deployment alongside cloud, on-device, and fully air-gapped options. This is essential for enterprises in regulated industries like healthcare, finance, and government. AssemblyAI is primarily a SaaS platform — its self-hosted option covers real-time streaming only and requires an upfront commercial commitment. Speechmatics scores 95% on G2 for regulatory compliance versus AssemblyAI's 80%.

Speechmatics delivers 500ms partial transcripts and sub-1-second final results in real-time streaming. On G2, Speechmatics scores 93% for low-latency processing versus AssemblyAI's 77% — a 16-percentage-point gap. For latency-sensitive applications like voice agents, live captioning, and real-time analytics, this difference is significant.

Yes. Speechmatics holds ISO 27001 certification, SOC2 Type II, HIPAA compliance, and full GDPR compliance. AssemblyAI also holds ISO 27001 and SOC 2 Type II and offers HIPAA BAAs. Speechmatics adds on-premises, on-device and air-gapped deployment options for security-conscious enterprises.

Yes. Speechmatics offers a straightforward REST API and WebSocket interface for real-time transcription. To help you evaluate the switch, new accounts get $100 in credit to get started. Our customer success team provides hands-on migration support, and G2 reviewers rate Speechmatics 95% for being a "Good Partner in doing business" versus AssemblyAI's 90%.

AssemblyAI lists transcription from $0.15/hr (Universal-2 and Universal-Streaming), $0.21/hr for Universal-3.5 Pro and $0.45/hr for Universal-3.6 Pro Realtime, with add-ons such as speaker diarization, PII redaction and summarization billed per hour on top. Speechmatics starts from $0.12/hr for Melia batch, with speaker diarization and custom dictionary included at no extra charge. See Speechmatics pricing for every model.

Yes. Speechmatics includes a dedicated Medical Model purpose-built for clinical documentation — trained on SNOMED CT terminology, FDA/MHRA drug names, and real clinical audio. It delivers up to 50% fewer critical errors compared to general models, with 96% medical term recall, available for real-time transcription across English, French, German, Spanish, Danish, and Norwegian. AssemblyAI offers medical terminology as a paid Medical Mode add-on rather than a dedicated medical model. See the Medical Model launch announcement and the Humetrix case study — where Speechmatics replaced Whisper for multilingual clinical transcription across 27 languages at the Paris 2024 Olympics.

Melia is Speechmatics’ new multilingual speech-to-text model with native code-switching across all 55+ supported languages in a single pass — no per-language model selection needed. It outperforms Deepgram, Microsoft, and AssemblyAI on most FLEURS language benchmarks, making it a strong fit for multilingual content, accented speakers, and global deployments. Priced from $0.12/hr for batch, it’s also the most affordable model in the Speechmatics range.

AssemblyAI's free tier needs no credit card and covers up to 185 hours of pre-recorded or 333 hours of streaming transcription. Speechmatics gives new accounts $100 in credit to get started, also with no card required.

All three offer real-time and batch speech-to-text APIs, so the choice usually comes down to accuracy on your own audio, language needs, deployment and total cost. AssemblyAI and Deepgram both bill speaker diarization as a paid add-on, while Speechmatics includes it at no extra charge and also offers on-device deployment. See our Speechmatics vs Deepgram comparison for the Deepgram side.