comet-ml--opik/apps/opik-documentation/documentation/fern/docs-v2/prompt_engineering/overview.mdx

---
headline: Prompt Library Overview | Opik Documentation
og:description: An overview of Opik's Prompt Library for versioning and managing
  the prompts behind your AI applications
og:site_name: Opik Documentation
og:title: Prompt Library Overview — Opik
title: Prompt Library Overview
---

The Prompt Library is the central place to manage every prompt your agent depends on. Version
them, iterate on new versions from the Opik UI or the SDK, and link the exact version that
produced a trace.

## Why use the Prompt Library

When prompts are hardcoded, every change requires a code change to update. There is no history
of what changed, no way to roll back quickly, and no clean way to compare alternative versions.

The Prompt Library gives you version control for the prompts that drive your agent. Push them to
Opik once, and from there you can compare versions, fetch a specific one, or always follow the
latest.

## Key features

- **Project-scoped prompts** — Every prompt lives inside a project, so different agents can have prompts with the same name without colliding.
- **Versioning by `v1`, `v2`, `v3`, …** — Each change creates a new immutable, sequentially numbered version. Fetch a specific one with the `version` selector (e.g. `"v3"`), or omit it to fetch the most recent.
- **Text and chat prompts** — Version simple string templates as well as multi-message chat templates with `{{variable}}` substitution.
- **Agent configuration in one place** — Prompts live alongside the rest of an agent configuration (model, parameters, tools) so a trace links back to the exact bundle that produced it.
- **Python and TypeScript SDKs** — Create, fetch, and render prompts from either language.

## How it works

1. **Define your prompts** — Use `create_prompt` / `create_chat_prompt` to send your prompts to Opik. This becomes `v1`.
2. **Fetch at runtime** — Call `get_prompt` / `get_chat_prompt` from inside a tracked function. The SDK returns the requested version and links it to the trace automatically.
3. **Iterate from the UI** — Edit the prompt and save a new version. If your code doesn't pin a `version`, the agent picks up the new version on its next fetch — otherwise update your code to point at the new version name.

## Next steps

- [Getting started](/development/prompt-library/getting-started) — Add the Prompt Library to your code in minutes
- [Text and chat prompts](/development/prompt-library/prompt-types) — When to use each, multimodal content, template engines, and searching
- [Version control](/development/prompt-library/version-control) — Create and compare versions
- [Prompt playground](/development/prompt-playground) — Test prompt variants side-by-side across models, without writing code