A prompt template is a parameterized prompt structure where certain values are replaced with variables at runtime. Instead of hardcoding user-specific data, context, or configuration directly into the prompt text, templates use placeholders like {{variable_name}} that are resolved when the prompt is fetched.
Templates separate the static structure of a prompt from its dynamic content. The template itself — the instructions, formatting rules, guardrails, and examples — is managed and versioned independently from the runtime data. This separation enables prompt engineers to iterate on prompt logic without touching application code, and developers to change the data flowing into prompts without modifying the prompt itself.
Common variable types include user context (name, role, preferences), retrieved documents for RAG pipelines, configuration parameters (output language, response length, tone), session-specific data (conversation history, previous responses), and environment flags (feature toggles, A/B test variants).
Variable interpolation — the process of replacing placeholders with actual values — typically happens server-side when the prompt is fetched via API. This ensures that the client application never needs to know the full prompt structure, maintaining a clean separation of concerns.
Effective template design follows several principles. Variables should have descriptive names that make the template self-documenting. Default values should be provided for optional variables. Validation rules should ensure required variables are always supplied, and templates should be tested with representative variable values to catch formatting issues.
Prompt management platforms typically provide a variable registry where teams can define, document, and validate the variables used across their prompt templates, preventing runtime errors from missing or malformed variable values.