Deepgram vs AssemblyAI: which speech-to-text API is better?

Neither is better for every job. For recorded English audio, AssemblyAI is the stronger pick: it lists at a lower price and scored a lower error rate on the independent Artificial Analysis index. For live voice agents and self-hosted deployments, Deepgram has the edge. All prices below were read on each vendor's pricing page on 27 October 2026.

AssemblyAI is cheaper on recorded audio

AssemblyAI's Universal-3.5 Pro lists at $0.21 per hour ¹, and its lower-cost Universal-2 at $0.15 per hour ². Deepgram's Nova-3 Monolingual lists at $0.258 per hour ³, about 1.23 times AssemblyAI's Pro price ⁴.

The speaker-label difference narrows the gap a little: Deepgram includes diarization on recorded audio, while AssemblyAI charges extra. Even so, AssemblyAI stays cheaper per hour. For the full price lists see how much Deepgram costs and how much AssemblyAI costs.

AssemblyAI scored better on accuracy

On Artificial Analysis's three-dataset index, AssemblyAI's Universal-3.5 Pro scored a 3.0 percent word error rate, against 5.2 percent for Deepgram's Nova-3 ^{10 11}. A two-point gap is large enough to matter. Each vendor's own benchmark favors itself: AssemblyAI reports 7.9 percent for Nova-3 ¹², while Deepgram reports 5.26 percent in its own launch tests ¹³. Neither publishes test audio, so lean on the independent figure and then test your own files. More in how accurate Deepgram is.

Deepgram wins on live speed and deployment

In Artificial Analysis's 2026 streaming benchmark, Deepgram's Flux returned a final transcript 0.020 seconds after speech ended, the fastest service tested ¹⁴. AssemblyAI's realtime model took 0.47 seconds to its first partial transcript ¹⁵. Flux also scored a higher error rate on partial results, 7.4 percent against 3.6 percent for ElevenLabs' realtime model ¹⁶, so speed is bought with some accuracy.

Deepgram's own comparison page recommends itself for batch and real-time transcription, hosted or self-hosted deployment, and a voice agent API on one platform ¹⁷. That is a vendor view, but self-hosting and regional endpoints are real differences if your data cannot leave your network.

It depends: which one fits your job

Privacy defaults differ. Deepgram retains requests to improve its models unless you opt out per request ¹⁸, and the opt-out gives zero data retention ¹⁹. AssemblyAI says pre-recorded transcription does not offer zero retention ²⁰.

What to do

1. Run the same 30 to 60 minutes of your own audio through both. Both have free credit or free hours, so the test costs nothing.
2. Score each with word error rate against corrected transcripts, and time live responses from your own servers.
3. Price a month at regular rates, with the add-ons you need.
4. Pick the winner for your audio, not the winner on a leaderboard.

Posts on Reddit and forums vary by workload and date, so use them for hints about edge cases, then verify. See the guide to Deepgram, the guide to AssemblyAI and the overview of speech recognition. If you are not building a product, free browser transcription at /audio-to-text may be all you need.