DictionaryEvaluation
Time to First Token (TTFT)
How long you wait before the AI starts replying, like the pause before someone begins to answer.
Definition
The time from sending a prompt until the model produces the first token of its response, the main driver of perceived responsiveness in chat and streaming interfaces. Model size, prompt length, thinking effort, hardware, and network conditions all affect it; streaming, faster models, shorter prompts, prompt caching, and lower effort reduce it.
Example
With streaming, text appears after 0.8 seconds (the TTFT) even though the full answer takes 12 seconds to finish.