Side by side

AssemblyAI vs Kaldi

Both stand on speech recognition software. Which one you can start free with, which one lets you read the code, and what each costs once you pay.

AssemblyAI

Free plan APISelf-hostedWeb

AssemblyAI offers a broad set of speech capabilities and usage-based plans, with a free tier subject to stated limits. Compare the language coverage and rates for each model to the needs of your application.

Visit AssemblyAI

Kaldi

Free plan AndroidLinuxMac+3

Kaldi offers a broad toolkit and model archives for speech recognition work, with commercial use permitted under Apache License 2.0. Its expert-oriented documentation and limited Windows support are important constraints to consider.

Visit Kaldi

The facts

	AssemblyAI	Kaldi
Free plan	Yes	Yes
Open source	Not published	Not published
Runs on	API, Self-hosted, Web	Android, Linux, Mac, Self-hosted, Web, Windows
Lowest paid plan	See the plans	Free or on request
Plans published	13	1
Maker	Not published	Not published
Website	assemblyai.com	kaldi-asr.org
On speech recognition software	#4 of 32	#8 of 32

AssemblyAI: what it does well

Speech features include diarization, summaries, and sentiment analysis.
States support for 99 languages.
Offers managed-cloud and self-hosted deployment.
Free tier includes audio credits.
Monthly billing is based on actual usage.

What to know first

Free tier has streaming and transcription limits.
Universal-3.5 Pro Realtime is listed for 18 languages.
Pay-as-you-go charges vary with usage.

Kaldi: what it does well

Apache License 2.0 permits commercial use
Includes example recipes for recognition systems
Models cover recognition, diarization, and speaker identification
Supports Android cross-compilation and WebAssembly

What to know first

Windows example scripts do not work
Windows compatibility is not actively maintained
Documentation is expert-oriented
Some example scripts use SRILM, not free for commercial use

Alternatives to AssemblyAI Alternatives to Kaldi The whole list