Why does Claude use XML tags in prompts?

Anthropic recommends XML tags because Claude's training data included structured documents with XML. Tags like , , and help Claude parse and follow each instruction independently.

What XML tags should I use for Claude prompts?

Common tags include , , , , , and . You can define your own tag names as long as they are consistent.

Does Claude 3.5 Sonnet work differently from Claude 3 Opus?

Both models follow XML-structured prompts well. Claude 3.5 Sonnet is faster and cheaper while Claude 3 Opus tends to follow nuanced instructions more carefully.

Claude Prompt Builder

Build structured system prompts for Anthropic Claude using XML tags.

Role / Persona

Task / Instruction

Context / Background

Constraints / Rules

Output Format

Examples

Assembled Prompt

0 tokens · 0 chars

Fill in the fields on the left to build your prompt...

Format: XML tags (Claude system prompt style)

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Learn More

guide:claude system prompts guide:prompt engineering basics

FAQ

Why does Claude use XML tags in prompts?: Anthropic recommends XML tags because Claude's training data included structured documents with XML. Tags like <role>, <task>, and <constraints> help Claude parse and follow each instruction independently.
What XML tags should I use for Claude prompts?: Common tags include <role>, <task>, <context>, <constraints>, <output_format>, and <examples>. You can define your own tag names as long as they are consistent.
Does Claude 3.5 Sonnet work differently from Claude 3 Opus?: Both models follow XML-structured prompts well. Claude 3.5 Sonnet is faster and cheaper while Claude 3 Opus tends to follow nuanced instructions more carefully.

Build well-structured prompts optimized for Anthropic Claude models. Uses XML tag formatting — the native format recommended by Anthropic for Claude system prompts. Fill in role, task, context, constraints, output format, and examples.