AssemblyAI vs Speechmatics

For call center workloads at scale, batch transcription rate is the dominant cost driver. Speechmatics charges $0.00215 per audio minute versus AssemblyAI at $0.0035 per audio minute, a difference of roughly 39% per minute that compounds heavily at high volume. On speaker diarizationdiarization - Splitting a transcript by speaker, so you can see who said what., Speechmatics includes it in the base rate while AssemblyAI adds roughly $0.000333 per audio minute, widening the total cost gap further for diarized call recordings. AssemblyAI counters with PII redaction as a paid add-on, which Speechmatics lacks entirely, and AssemblyAI's concurrency ceiling of 200 or more async jobs is notably higher than Speechmatics' 50 real-time sessions. Sentiment analysis is available on both. Even so, the combination of a lower batch price and included diarization tips the scale.

For developers building metered transcription products, batch pricing is the heaviest factor. Speechmatics charges $0.00215 per audio minute versus AssemblyAI at $0.0035, a meaningful 39% cost difference that compounds at scale. On SDKs, Speechmatics offers four official options (Python, JavaScript,.NET, Rust) compared to AssemblyAI's two (Python, JavaScript/Node), giving Speechmatics a broader integration surface. Both tools offer websocket streaming and word-level timestampsword-level timestamps - The API reports exactly when each word is spoken in the audio, for subtitles and highlighting.. On audio format flexibility, AssemblyAI supports 30+ formats versus Speechmatics's nine listed formats, giving AssemblyAI an edge there. However, the decisive pricing gap and SDK breadth advantage for Speechmatics outweigh the format flexibility difference.

The available facts cover API-level attributes such as batch pricing, word error rate, language support, and SDK availability. None of the five attributes that matter for this dictation use case are addressed: platform coverage for voice typing apps, whether audio is processed on device or in the cloud, AI formatting and editing features, one-time versus subscription app pricing, and app integrations. Both AssemblyAI and Speechmatics are cloud API providers, and no facts distinguish them on any of these dictation-specific dimensions. Without information on local processing, dictation platform support, or app-level pricing models, no winner can be determined.

Both tools offer a HIPAA BAAHIPAA BAA - A signed Business Associate Agreement that lets you handle protected health information under US healthcare privacy law., SOC 2 Type II, custom vocabulary, and self-host options, so those attributes do not separate them. The deciding factor is PII redaction, weighted 4 out of 5. AssemblyAI provides PII redaction as a paid add-on at about $0.08 per hour, while Speechmatics does not offer PII redaction at all. In a clinical setting under US healthcare privacy law, the ability to automatically redact patient identifiers is a meaningful compliance capability. Speechmatics simply cannot match it. That absence is a genuine gap for this use case, even though its batch pricing at $0.00215 per audio minute is lower than AssemblyAI's $0.0035.

For recorded meetings, speaker diarizationdiarization - Splitting a transcript by speaker, so you can see who said what. carries the heaviest weight. Speechmatics includes diarization in its base price, while AssemblyAI charges a small extra per-minute fee, giving Speechmatics a slight edge on that cost. However, AssemblyAI pulls ahead on the next two attributes. Both tools offer summarization, so that is even. On languages, AssemblyAI supports 99 versus Speechmatics at 56, a meaningful gap for multilingual meeting content. On file handling, AssemblyAI accepts files up to 5 GB or 10 hours, while Speechmatics caps request-body uploads at 1 GB, making AssemblyAI more capable for long recordings. Word-level timestamps are available from both. The language breadth and file-size advantage tip the balance to AssemblyAI despite the diarization add-on cost.

Both AssemblyAI and Speechmatics offer a self-hostself-host - Run the software on your own servers instead of the vendor’s cloud. or on-prem option. However, no data is available on open weights license, hardware requirements, project maintenance status, or model parameters for either tool. Since the heaviest attribute (self-host option, weight 5/5) is equal for both, and the remaining decisive attributes are simply not published for either tool, there is no basis to favor one over the other.

Both tools offer WebSocket streaming APIs, so that factor cancels out. AssemblyAI publishes a vendor-claimed streaming latency of 150 ms, while Speechmatics provides no published figure, giving AssemblyAI a clear edge on the heaviest deciding attribute. On streaming price, AssemblyAI charges $0.0075 per audio minute versus no published rate for Speechmatics, making AssemblyAI the only option with a known streaming price. On concurrencyconcurrency - How many phone calls the platform can handle at the same time., AssemblyAI supports 100 new streams per minute on the base plan compared to Speechmatics at 50 real-time sessions, a meaningful advantage for scaling voice agents. Both tools offer custom vocabulary boosting, so that attribute is even. The latency and concurrency advantages tip the decision despite AssemblyAI's higher streaming per-minute cost.