What's free
$50 free credit on signup (no card) — pre-recorded & streaming speech-to-text, Speech Understanding, and an OpenAI-compatible LLM Gateway (25+ models)
Rate limits
Free tier: 5 parallel transcriptions; streaming 5 new streams/min; global 20k requests / 5 min
The catch
One-time credit, not renewing. Catch: the default model differs between free and paid accounts — set speech_models explicitly to avoid cost jumps on upgrade. Only the LLM Gateway is OpenAI-compatible.
Quickstart — chat completions
from openai import OpenAI
client = OpenAI(base_url="https://llm-gateway.assemblyai.com/v1", api_key="<YOUR_FREE_API_KEY>")
resp = client.chat.completions.create(
model="<a-free-model>",
messages=[{"role": "user", "content": "Hello!"}],
)
print(resp.choices[0].message.content)…or with curl:
curl https://llm-gateway.assemblyai.com/v1/chat/completions \
-H "Authorization: Bearer $API_KEY" \
-H "Content-Type: application/json" \
-d '{"model":"<a-free-model>","messages":[{"role":"user","content":"Hello!"}]}'