---
source: https://iinventedlight.com/library/notes/nextjs-use-server.md
title: "The use server directive and Server Functions"
license: CC-BY-4.0
license_url: https://creativecommons.org/licenses/by/4.0/
source_license: "MIT (vercel/next.js); prose restates cited source lines in own words"
license_family: nextjs-mit
attribution: "Summary by iinventedlight (AI-assisted). Sources: Next.js docs, use server, MIT (vercel/next.js); Next.js docs, Mutating data, MIT (vercel/next.js). Copyright (c) 2025 Vercel, Inc. MIT (https://raw.githubusercontent.com/vercel/next.js/canary/license.md)."
author: "iinventedlight (synthesis of cited sources); text drafted with AI assistance"
date: 2026-11-09
status: published
approved_by: "Cole Withington, 2026-11-09 13:04 PT: \"Yes, publish all 33 Next.js drafts\""
checked_on: 2026-11-09
as_of: 2026-11-09
confidence: medium
untested: "No Next.js app was run for this note; only the fetched documentation pages were read."
category: coding-references
topic_area: "code-web: Next.js mutations"
tags: [nextjs, use-server, server-actions]
client: Librarian
sources:
  - id: S1
    title: "use server"
    publisher: Next.js docs
    url: https://nextjs.org/docs/app/api-reference/directives/use-server
    accessed: 2026-11-09
    license: "MIT (vercel/next.js)"
  - id: S2
    title: "Mutating data"
    publisher: Next.js docs
    url: https://nextjs.org/docs/app/getting-started/mutating-data
    accessed: 2026-11-09
    license: "MIT (vercel/next.js)"
---
# The use server directive and Server Functions

**Answer:** `"use server"` marks a function or file to run on the server. Those Server Functions can be imported into Client Components; in mutation contexts they are Server Actions.

## Directive

The `use server` directive designates a function or file to be executed on the server. All functions in a `"use server"` file run on the server.

## Calling from the client

Create Server Functions in a dedicated file, then import them into Client Components to execute them.

## Return values

Server Function return values are serialized and sent to the client. Return only what the UI needs.

## See also

- [nextjs-forms](https://iinventedlight.com/library/notes/nextjs-forms/)
- [nextjs-revalidating](https://iinventedlight.com/library/notes/nextjs-revalidating/)

## Claims

- id: C1
  claim: use server runs code on the server.
  source: S1
  evidence: "The `use server` directive designates a function or file to be executed on the **server"

- id: C2
  claim: Import Server Functions into Client Components.
  source: S1
  evidence: "To use Server Functions in Client Components you need to create your Server Functions in"

- id: C3
  claim: Return values are serialized to the client.
  source: S1
  evidence: "Server Function return values are serialized and sent to the client."

- id: C4
  claim: Mutation context calls them Server Actions.
  source: S2
  evidence: "In an `action` or mutation context, they are also called **Server Actions**."

## Sources

- [S1] use server. Next.js docs. https://nextjs.org/docs/app/api-reference/directives/use-server . License: MIT (vercel/next.js). Accessed 2026-11-09.

- [S2] Mutating data. Next.js docs. https://nextjs.org/docs/app/getting-started/mutating-data . License: MIT (vercel/next.js). Accessed 2026-11-09.


License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted). Copyright (c) 2025 Vercel, Inc. Sources: Next.js docs (vercel/next.js on GitHub / nextjs.org), MIT (https://raw.githubusercontent.com/vercel/next.js/canary/license.md). Text was condensed and changed from the originals.

---

Agents: [/agents.md](/agents.md) | [/.well-known/agent-library.json](/.well-known/agent-library.json).