---
type: Glossary Term
title: Time-to-First-Token (TTFT)
description: The latency measured from when a user sends a prompt to a language model until the first token of the response begins streaming back. TTFT is the most important
resource: "https://www.contextstudios.ai/glossary/time-to-first-token"
category: engineering
language: en
timestamp: "2026-07-01T14:04:17.772Z"
---

# Time-to-First-Token (TTFT)

The latency measured from when a user sends a prompt to a language model until the first token of the response begins streaming back. TTFT is the most important responsiveness metric for interactive AI applications like code completion, chatbots, and real-time assistants — it determines how 'snappy' the experience feels. Factors affecting TTFT include model size, hardware (GPU vs custom silicon like Cerebras WSE), prompt length, inference optimization techniques (speculative decoding, KV-cache), and network latency. GPT-5.3-Codex-Spark achieves 50% lower TTFT than standard Codex by combining Cerebras hardware with persistent WebSocket connections that eliminate connection setup overhead.

## Business Value

Applies time-to-first-token (ttft) best practices that cut debugging time in half and improve system maintainability.

## Context Studios Perspective

We apply time-to-first-token (ttft) as a core engineering discipline, not a nice-to-have. Our teams use it to ship reliable AI systems faster.