AssemblyAI - Speech to Text API
Voice recognition software
Deep learning software
- Features
- Ease of use
- Ease of management
- Quality of support
- Affordability
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What is AssemblyAI - Speech to Text API
AssemblyAI Speech to Text API is a cloud-based speech recognition service that converts audio and video into text via developer APIs. It targets software teams building transcription, call analytics, meeting capture, media indexing, and other speech-enabled workflows. The platform also exposes higher-level speech intelligence features (for example, speaker diarization and content extraction) that can be composed into applications. It is typically consumed as an API rather than an end-user transcription application.
Developer-first API integration
AssemblyAI is delivered primarily through APIs and documentation intended for engineering teams. This fits product teams that want to embed transcription into their own applications rather than adopt a standalone UI. Common integration patterns include asynchronous transcription jobs and webhook-based status updates. The API-centric approach supports building custom workflows around speech data.
Speech intelligence add-ons
Beyond basic speech-to-text, the service provides optional features that enrich transcripts, such as speaker diarization and other metadata extraction capabilities. These features reduce the need to stitch together multiple services for common downstream tasks like search, analytics, and content moderation. For teams building domain workflows, having these capabilities in the same API can simplify architecture. It also helps standardize output formats across features.
Scales for production workloads
As a managed cloud API, the product is designed for programmatic, repeatable processing of large volumes of audio. This is relevant for contact center recordings, media libraries, and other batch transcription use cases. Centralized service operation shifts model hosting and infrastructure management away from the customer. It can be deployed without maintaining GPU infrastructure in-house.
Cloud dependency and data handling
Using the API typically requires sending audio to a third-party cloud service, which can be a constraint for regulated or data-residency-sensitive environments. Security, retention, and compliance requirements may require additional contractual and technical controls. Some organizations may prefer on-premises or fully self-hosted options for sensitive audio. Network connectivity and upload time can also affect end-to-end latency.
Accuracy varies by domain
Speech recognition performance can vary based on accents, background noise, overlapping speakers, and specialized vocabulary. Domain-specific terminology (for example, medical or legal) may require evaluation and potential customization or post-processing. Teams should benchmark with representative audio rather than rely on generic accuracy expectations. Error patterns can materially affect downstream analytics and automation.
Cost at high volumes
API pricing is typically usage-based, so costs can increase quickly with long recordings or large-scale ingestion. This can be a limiting factor for always-on transcription, large media archives, or high-frequency call recording. Budgeting often requires careful forecasting and monitoring of minutes processed and feature usage. Some workloads may need batching, summarization, or selective transcription to control spend.
Plan & Pricing
Pricing model: Pay-as-you-go Free tier/trial: $50 in credits on sign-up (equivalent to up to 185 hours pre-recorded or 333 hours streaming as stated on the official Pricing page). Free credit available to new accounts; LLM Gateway not available on the free tier.
Example costs (key Speech-to-Text models & add-ons) — billed per hour, prorated to the second:
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Pre-recorded Speech-to-Text:
- Universal-3 Pro — $0.21 / hr.
- Universal-2 — $0.15 / hr.
- Prompting (add-on) — $0.05 / hr.
- Keyterms Prompting (add-on) — $0.05 / hr.
- Speaker Diarization (add-on) — $0.02 / hr.
-
Streaming Speech-to-Text:
- Universal-Streaming — $0.15 / hr.
- Universal-Streaming Multilingual — $0.15 / hr.
- Keyterms Prompting (streaming add-on) — $0.04 / hr.
-
Speech Understanding (audio intelligence) — (examples):
- Speaker Identification — $0.02 / hr.
- Translation — $0.06 / hr.
- Custom Formatting — $0.03 / hr.
- Entity Detection — $0.08 / hr.
- Sentiment Analysis — $0.02 / hr.
- Auto Chapters — $0.08 / hr.
- Key Phrases — $0.01 / hr.
- Topic Detection — $0.15 / hr.
- Summarization — $0.03 / hr.
-
Guardrails / Safety features (examples):
- Profanity Filtering — $0.01 / hr.
- PII Audio Redaction — $0.05 / hr.
- PII Redaction (text) — $0.08 / hr.
- Content Moderation — $0.15 / hr.
-
LLM Gateway (tokenized pricing examples):
- GPT-5.2 — $1.75 / 1M input tokens; $14.00 / 1M output tokens.
- GPT-5.1 — $1.25 / 1M input; $10.00 / 1M output.
- (Multiple other LLMs listed with per-1M-token input/output rates on the pricing page.)
Discounts / enterprise: Volume discounts and enterprise/tiered pricing are available by contacting AssemblyAI sales (custom pricing, rate limits, enhanced concurrency, self-hosting options).
Billing notes: Rates are listed per hour but pro-rated to the second. Multichannel audio is billed per channel (each channel transcribed and billed separately).
Seller details
AssemblyAI, Inc.
San Francisco, CA, USA
2017
Private
https://www.assemblyai.com/
https://x.com/AssemblyAI
https://www.linkedin.com/company/assemblyai/
