Ultrafield vs AssemblyAI.
Considering Ultrafield as an AssemblyAI alternative? A like-for-like read on published rates, models and billing — including the two categories where AssemblyAI is cheaper. List pay-as-you-go pricing, verified August 2026.
Published rates, per hour of audio.
Where each one actually wins.
AssemblyAI is the closest competitor to us on price, and a comparison that claimed a clean sweep would not survive five minutes on their pricing page. So: they are cheaper in two places, and we are cheaper in the rest.
Where we are cheaper
Batch transcription at every tier. Whisper large-v3-turbo at $0.07 per hour is roughly half Universal-2 at $0.15, and ASR-1 at $0.13 is well under Universal-3.5 Pro at $0.21. Flagship streaming is $0.19 against $0.45. You also get open-weight models you can name explicitly rather than a single proprietary engine, which keeps the option to move.
Where they are cheaper
Entry-tier streaming: Universal-Streaming is $0.15 per hour against our $0.19 on ASR-1. Our Whisper turbo stream at $0.11 undercuts it, but flagship-to-flagship they win. And async speaker labels are a $0.02 per hour add-on against our $0.06 diarization stage — three times cheaper. If diarization dominates your bill, that is decisive.
One thing to measure yourself
Both vendors bill per second, so headline rates compare directly. But AssemblyAI documents that streaming is billed on session duration — the time the WebSocket stays open, including idle — rather than on audio sent. We bill processed audio. For a voice agent with long pauses that can matter more than the rate itself, and it will not show up in any comparison table, including this one. Run a real session and check the invoice.
When they are the better choice.
Universal-Streaming is $0.15/hr against our $0.19 on ASR-1. Our Whisper turbo stream at $0.11 undercuts it, but on flagship-to-flagship they win.
Their standard async speaker labels are a $0.02/hr add-on. Ours is a $0.06/hr stage. If diarization dominates your bill, that gap matters.
Years of production use, broad SDK coverage, LeMUR and an established audio-intelligence feature set.
Their realtime stack ships today. Our Realtime API is on the roadmap, not generally available.
What each vendor runs.
Moving over, without a rewrite.
Our audio endpoints follow OpenAI conventions for routes, Bearer auth, errors and usage reporting.
Universal-2 maps most closely to Whisper large-v3-turbo on cost, or ASR-1 where accuracy on difficult audio matters more.
Their speaker_labels flag becomes a named diarization stage on the same job, metered on its own.
The winner depends on your model tier and how much diarization you run. Run both on a slice of traffic before you migrate.
Questions people actually ask.
Is Ultrafield a good AssemblyAI alternative?
If you want open-weight models, one composable pipeline, and the lowest possible per-hour transcription cost, yes — Whisper large-v3-turbo at $0.07/hr is roughly half AssemblyAI Universal-2 at $0.15. If your workload is dominated by entry-tier streaming or by async speaker labels, AssemblyAI is currently cheaper and this page says where.
Is Ultrafield cheaper than AssemblyAI?
On batch transcription, yes at every tier: $0.07/hr on Whisper turbo or $0.13 on ASR-1 against $0.15 for Universal-2 and $0.21 for Universal-3.5 Pro. On streaming it depends — our turbo stream is $0.11 against their $0.15, but our ASR-1 stream is $0.19, which is more. On async diarization they are cheaper: $0.02/hr against our $0.06.
Which is cheaper for transcription plus diarization?
It depends on the model tier. Whisper turbo plus diarization is $0.13/hr against AssemblyAI Universal-2 plus speaker labels at $0.17. ASR-1 plus diarization is $0.19, which is more than their $0.17. Price it against your own mix rather than a headline rate.
How does streaming billing differ?
Both vendors bill per second. AssemblyAI documents that streaming is billed on session duration — the time the WebSocket is open, including idle time — rather than on audio sent. We bill processed audio. For conversational products with long pauses that difference can matter more than the headline rate, so measure it on a real session.
What do I gain by switching?
Open-weight models you can name explicitly and are not locked into, a single composable pipeline where diarization, speaker ID, entities, sentiment and language-model processing all run on one job, and lower per-hour cost on batch at every tier.
When should I stay on AssemblyAI?
If you need a generally available voice-agent product today, if entry-tier streaming is the bulk of your spend, or if async speaker labels dominate your bill. Their feature surface is also more mature, so if you depend on something specific there, check we have an equivalent before you plan a migration.
Price it against your own audio.
The winner depends on your model tier and how much diarization you run. Send us a representative workload and we will tell you honestly which way it goes.
Rates verified august 2026 from published list pricing