Time to First Token
Definition
Time to first token measures the waiting time from the defined request start to the first output text unit.
The measured duration from the defined request start to receiving the first output token of a generative service.
Simply explained
How long do you wait until the answer starts? This means the first text block, not the time until the entire answer is finished.
Why it matters in practice
The term contributes to secure, maintainable, and high-performance web applications as well as resilient technical decisions.
Example from business
A support assistant measures TTFT separately from total duration and tokens per second.
Limits and pitfalls
- Start point, queue, network, and caching must be defined; low TTFT says nothing about answer quality.
Origin & history
TTFT became an important perceived latency metric with streamed language model APIs.
Use in mid-sized companies
- Possible application: A support assistant measures TTFT separately from total duration and tokens per second.
Frequently asked questions
What does time to first token mean?
The measured duration from the defined request start to receiving the first output token of a generative service. What should you watch out for? Start point, queue, network, and caching must be defined; low TTFT says nothing about answer quality.
Sources
- GenAI-Perf metrics · NVIDIA, GenAI-Perf metrics
Source checked on 10.10.2026. Editorial application examples are hypothetical; no evidence of real customer results.
Editorially reviewed on: