---
title: "User Message"
description: "A user message is a message in a chat-style LLM API that represents input from the end user or calling application on the user's behalf. It usually contains the task request, question, provided data, constraints, or follow-up information."
canonical_url: "https://promptmetheus.com/resources/llm-knowledge-base/user-message"
---

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A user message is a message in a chat-style LLM API that represents input from the end user or calling application on the user's behalf. It usually contains the task request, question, provided data, constraints, or follow-up information.

In a conversation, user messages are distinct from:

- a [system message](https://promptmetheus.com/resources/llm-knowledge-base/system-message), which sets high-level behavior or policy;
- a developer instruction, which may define application-specific behavior;
- an [assistant message](https://promptmetheus.com/resources/llm-knowledge-base/assistant-message), which represents the model's prior or generated response; and
- tool messages, which return results from tool calls.

User messages are important for instruction hierarchy. A user can request a task, but the request should not override higher-priority system or developer constraints. This matters for safety, data access, and [prompt injection attacks](https://promptmetheus.com/resources/llm-knowledge-base/prompt-injection-attack).

In [context engineering](https://promptmetheus.com/resources/llm-knowledge-base/context-engineering), user messages should be preserved accurately when they contain task requirements, approvals, or corrections. They may be summarized during [context compaction](https://promptmetheus.com/resources/llm-knowledge-base/context-compaction), but important constraints should remain explicit.

OpenAI's help article on moving from completions to chat messages explains that each message has a role and content, including the user role, in [Moving from Completions to Chat Completions](https://help.openai.com/en/articles/7042661).

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