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Official agent skill

Copy To Output Directory

by dotnet in dotnet/skills

Choosing an MSBuild CopyToOutputDirectory / CopyToPublishDirectory mode: Never, PreserveNewest, Always, and IfDifferent (MSBuild 17.13+), plus $(SkipUnchangedFilesOnCopyAlways).

OfficialMITAuto-check passed

Install Copy To Output Directory

skills CLI
$ npx skills add dotnet/skills --skill copy-to-output-directory -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install dotnet/skills copy-to-output-directory --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/dotnet/skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/plugins/dotnet-msbuild/skills/copy-to-output-directory .claude/skills/copy-to-output-directory && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
copy-to-output-directory
GitHub stars
5.6k
Used in
1 other repo
Token cost
~1.8k tokens
SKILL.md length
809 words
Files
1
Skills in repo
93
Repo updated
First seen
Licence
MIT

At a glance

Choosing an MSBuild CopyToOutputDirectory / CopyToPublishDirectory mode: Never, PreserveNewest, Always, and IfDifferent (MSBuild 17.13+), plus $(SkipUnchangedFilesOnCopyAlways).

  • : removing the per-build Always copy perf hit
  • SKILL.md covers Overview, Why Always is usually the…, IfDifferent: copy when… and Globally softening Always with…, plus 3 more sections
  • Calls dotnet
  • Resetting output files mutated between builds

What it does

Copy To Output Directory is an agent skill from dotnet/skills, published by the product's own GitHub organization. Choosing an MSBuild CopyToOutputDirectory / CopyToPublishDirectory mode: Never, PreserveNewest, Always, and IfDifferent (MSBuild 17.13+), plus $(SkipUnchangedFilesOnCopyAlways). USE FOR: removing the per-build Always copy perf hit; resetting output files mutated between builds. DO NOT USE FOR: general incremental-build diagnosis (use incremental-build); non-MSBuild build systems.

Its SKILL.md is about 1.8k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It works with .NET. The repository describes itself as: Repository for skills to assist AI coding agents with .NET and C. The licence is MIT.

When your agent uses it

  • : removing the per-build Always copy perf hit
  • Resetting output files mutated between builds
  • : general incremental-build diagnosis (use incremental-build)
  • Non-MSBuild build systems

Example prompts

  • “/copy-to-output-directory”

What it can do on your machine

Read from SKILL.md and the folder at commit 3d38ac3. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • dotnet

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Copy To Output Directory loads about 1.8k tokens when it runs. Until then it costs about 102 tokens; SKILL.md has 809 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~102
When it runs · the whole SKILL.md, loaded when a task matches
~1.8k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from dotnet/skills at commit 3d38ac3, republished under its MIT licence (© dotnet). 809 words, ~1,810 tokens.

Download SKILL.mdSave it as .claude/skills/copy-to-output-directory/SKILL.md (or your agent's skills folder).
name
copy-to-output-directory
description
Choosing an MSBuild CopyToOutputDirectory / CopyToPublishDirectory mode: Never, PreserveNewest, Always, and IfDifferent (MSBuild 17.13+), plus $(SkipUnchangedFilesOnCopyAlways). USE FOR: removing the per-build Always copy perf hit; resetting output files mutated between builds. DO NOT USE FOR: general incremental-build diagnosis (use incremental-build); non-MSBuild build systems.
license
MIT

Choosing a CopyToOutputDirectory Mode

Overview

The CopyToOutputDirectory metadata (and its publish counterpart CopyToPublishDirectory) controls whether an item — Content, None, EmbeddedResource, or Compile — is copied next to your build output, and under what conditions the copy happens. Picking the wrong mode causes either stale files in bin/ or an unnecessary per-build performance hit.

As of MSBuild 17.13 / .NET SDK 9.0.2xx there are four values:

ModeCopies when…Incremental costTypical use
Never (default)NeverNoneFiles not needed at runtime
PreserveNewestSource is newer than destination (or destination missing)Cheap (timestamp check)The common case — source files you edit
AlwaysEvery build, unconditionallyExpensive — copies on every build even in no-op buildsLegacy workaround; avoid (see below)
IfDifferentSource differs from destination in either direction (newer or older, or size differs, or destination missing)Cheap (timestamp + size check)Destination may be mutated between builds
xml
<ItemGroup>
  <None Include="appsettings.json" CopyToOutputDirectory="PreserveNewest" />
  <None Include="testdata\seed.db"  CopyToOutputDirectory="IfDifferent" />
</ItemGroup>

You can use either the attribute form shown above or the child-element form:

xml
<None Include="testdata\seed.db">
  <CopyToOutputDirectory>IfDifferent</CopyToOutputDirectory>
</None>

Why Always is usually the wrong choice

Always re-copies the file on every build, including otherwise-clean incremental/no-op builds. On projects with many or large content files this is a measurable, recurring cost and a common cause of "why is my no-op build not instant?" reports.

Historically Always was the only way to handle a specific scenario: the destination file can change between builds — for example an SQLite database, a storage/state file, or a config file that a test run mutates. With PreserveNewest, if the destination is modified (making its timestamp newer than the source) MSBuild will not restore the original source file, because the source is no longer newer. People reached for Always to force the file back into a known-good state — paying the copy cost on every build as a side effect.

IfDifferent: copy when different, in either direction

IfDifferent is the targeted fix for that scenario. It copies the source over the destination whenever MSBuild considers the two different — whether the source is newer or older than the destination, whether the size differs, or the destination is missing — and skips the copy when the destination is unchanged per MSBuild's heuristic.

Under the hood the _CopyDifferingSourceItemsToOutputDirectory target uses the Copy task with SkipUnchangedFiles="true". That "unchanged" check is a heuristic: it compares last-write timestamp and file size only — not a content hash — so a destination that was edited to the same size and timestamp as the source is treated as unchanged and is not re-copied. In practice this restores a mutated destination back to the source version on the next build (the reason people reached for Always) while avoiding the unconditional per-build copy.

Use IfDifferent when:

  • A test run or the app itself writes to the copied file (databases, caches, state/storage files, editable config) and you want each build to reset it to the source version.
  • You were using Always purely as a "keep the output in sync with the source" mechanism, not because you truly need a copy on every single build.
xml
<ItemGroup>
  <!-- Reset the fixture DB to the source copy whenever it has drifted,
       but don't pay a copy on every no-op build. -->
  <None Include="fixtures\catalog.db" CopyToOutputDirectory="IfDifferent" />
</ItemGroup>
Show full SKILL.md (320 more words)Show less

Globally softening Always with $(SkipUnchangedFilesOnCopyAlways)

If you have an existing codebase full of CopyToOutputDirectory="Always" items and want the performance benefit without editing every item, set the property:

xml
<PropertyGroup>
  <SkipUnchangedFilesOnCopyAlways>true</SkipUnchangedFilesOnCopyAlways>
</PropertyGroup>

This makes the _CopyOutOfDateSourceItemsToOutputDirectoryAlways target pass SkipUnchangedFiles="true" to its Copy task, so Always items are only copied when they actually differ — effectively giving Always the same skip-unchanged behavior as IfDifferent.

  • Default is false for backwards compatibility (classic Always = copy every build).
  • Set it in Directory.Build.props to opt an entire repo in at once.
  • Prefer converting individual items to IfDifferent when you can; use this property when a bulk, non-invasive opt-in is more practical.

How the modes flow through the build

GetCopyToOutputDirectoryItems buckets each item by its CopyToOutputDirectory value. Three copy targets then do the work as dependencies of _CopySourceItemsToOutputDirectory (which is itself invoked by CopyFilesToOutputDirectory):

  • _CopyOutOfDateSourceItemsToOutputDirectory — PreserveNewest items (incremental via Inputs/Outputs timestamp comparison).
  • _CopyOutOfDateSourceItemsToOutputDirectoryAlways — Always items (unconditional copy unless $(SkipUnchangedFilesOnCopyAlways) is true).
  • _CopyDifferingSourceItemsToOutputDirectory — IfDifferent items (SkipUnchangedFiles="true").

All copied files are registered in FileWrites, so dotnet clean removes them.

Transitive copy: items marked Always, PreserveNewest, or IfDifferent also flow to referencing projects through ProjectReference (via _CopyToOutputDirectoryTransitiveItems). Never items do not. IfDifferent participates in ClickOnce publish item collection alongside Always/PreserveNewest.

Version requirement

IfDifferent and $(SkipUnchangedFilesOnCopyAlways) require MSBuild 17.13 or later (.NET SDK 9.0.2xx+ / Visual Studio 2022 17.13+). On older toolsets the value is not recognized: it will not match the Always/PreserveNewest/IfDifferent conditions in the common targets, so the item is silently not copied. Gate usage on the toolset if you must support older SDKs, or require the minimum SDK via global.json.

Quick decision guide

  • Don't need the file at runtime → Never (or omit — it's the default).
  • Normal source file you edit → PreserveNewest.
  • Destination gets mutated between builds and must be reset to the source → IfDifferent.
  • You truly need a fresh copy on literally every build → Always (rare).
  • Stuck with lots of legacy Always and want the perf win without edits → keep Always but set $(SkipUnchangedFilesOnCopyAlways)=true.

© dotnet, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in plugins/dotnet-msbuild/skills/copy-to-output-directory of dotnet/skills.

Open the folder on GitHubat commit 3d38ac3

Used in 1 other repository

We found 2 copies of this SKILL.md (exact, near-identical or edited) in other folders, from 1 other GitHub owner. This page covers the copy in dotnet/skills, which our catalogue first saw on October 7, 2026.

Compare with similar skills

Copy To Output Directory next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

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Speckit ConstitutionWeihanLi/WeihanLi.Common24211 repos~2.1kAutomated safety check: PassApache-2.0
Copilot Session Failure Analysisdotnet/maui23k—~3.4kAutomated safety check: PassMIT
Update .NET OS Packagesdotnet/core22k—~2.3kAutomated safety check: PassMIT

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Works with

Questions about Copy To Output Directory

What does Copy To Output Directory do?

Choosing an MSBuild CopyToOutputDirectory / CopyToPublishDirectory mode: Never, PreserveNewest, Always, and IfDifferent (MSBuild 17.13+), plus $(SkipUnchangedFilesOnCopyAlways). Copy To Output Directory is an agent skill from dotnet/skills, published by the product's own GitHub organization.13+), plus $(SkipUnchangedFilesOnCopyAlways).

When should I use Copy To Output Directory?

Copy To Output Directory fits situations like: : removing the per-build Always copy perf hit; resetting output files mutated between builds; : general incremental-build diagnosis (use incremental-build); non-MSBuild build systems.

How do I install Copy To Output Directory in Claude Code?

Run `npx skills add dotnet/skills --skill copy-to-output-directory -a claude-code`. Or copy the skill folder (plugins/dotnet-msbuild/skills/copy-to-output-directory in dotnet/skills) into .claude/skills/copy-to-output-directory in your project. Claude Code loads it when a task matches its description.

How do I install Copy To Output Directory in Codex?

Run `npx skills add dotnet/skills --skill copy-to-output-directory -a codex`. Or copy the skill folder (plugins/dotnet-msbuild/skills/copy-to-output-directory in dotnet/skills) into .agents/skills/copy-to-output-directory in your project. Codex loads it when a task matches its description.

Can I use Copy To Output Directory in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add dotnet/skills --skill copy-to-output-directory -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/copy-to-output-directory, .gemini/skills/copy-to-output-directory, .github/skills/copy-to-output-directory and .opencode/skills/copy-to-output-directory in your project.

What does Copy To Output Directory need to run?

Going by SKILL.md and its folder, Copy To Output Directory needs the command-line tools its instructions call (dotnet).

Does Copy To Output Directory access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Copy To Output Directory safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Copy To Output Directory use?

Copy To Output Directory is published under the MIT licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Copy To Output Directory use?

About 1.8k tokens (SKILL.md is roughly 7.2k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Copy To Output Directory?

Skills that share tags, products or a category with Copy To Output Directory: Minimax DOCX (poco-ai/poco-claw, 1.4k stars), Microsoft Skill Creator (MicrosoftDocs/mcp, 1.9k stars), Speckit Constitution (WeihanLi/WeihanLi.Common, 242 stars) and Copilot Session Failure Analysis (dotnet/maui, 23k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Copy To Output Directory?

dotnet (a GitHub organization, an official publisher) maintains it in dotnet/skills, which has 5,585 GitHub stars. The repository holds 93 skills in this directory. The repository was last updated on October 9, 2026.

Source: dotnet/skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.