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The --filter (or -F) flag selects packages in a monorepo by pattern. Patterns match package names or package paths, with full glob syntax. bun install and bun outdated support --filter, and you can use it to run scripts in multiple packages at once.

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Matching

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Package Name --filter <pattern>

Name patterns select packages by the name field in package.json. For example, if you have packages pkg-a, pkg-b and other, you can match all of them with *, only pkg-a and pkg-b with pkg*, and a specific package with its full name.

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Package Path --filter ./<glob>

Path patterns start with ./ and select all packages in directories matching the pattern. For example, to match all packages in subdirectories of packages, use --filter './packages/**'. To match the package in packages/foo, use --filter ./packages/foo.

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bun install and bun outdated

By default, bun install installs dependencies for every package in the monorepo. To install dependencies for specific packages, use --filter. Given a monorepo with workspaces pkg-a, pkg-b, and pkg-c under ./packages:
terminal
# Install dependencies for all workspaces except `pkg-c`
bun install --filter '!pkg-c'

# Install dependencies for packages in `./packages` (`pkg-a`, `pkg-b`, `pkg-c`)
bun install --filter './packages/*'

# Save as above, but exclude the root package.json
bun install --filter '!./' --filter './packages/*'
Similarly, bun outdated displays outdated dependencies for all packages in the monorepo, and --filter restricts the command to a subset of them:
terminal
# Display outdated dependencies for workspaces starting with `pkg-`
bun outdated --filter 'pkg-*'

# Display outdated dependencies for only the root package.json
bun outdated --filter './'
See bun install and bun outdated.

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Running scripts with --filter

Use the --filter flag to execute scripts in multiple packages at once:
terminal
bun --filter <pattern> <script>
Say you have a monorepo with two packages: packages/api and packages/frontend, both with a dev script that starts a local development server. Normally, you would open two terminal tabs, cd into each package directory, and run bun dev:
terminal
cd packages/api
bun dev

# in another terminal
cd packages/frontend
bun dev
Using --filter, you can run the dev script in both packages at once:
terminal
bun --filter '*' dev
Both scripts run in parallel, and a terminal UI shows their respective outputs:
Terminal Output

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Running scripts in workspaces

Filters respect your workspace configuration: if your package.json specifies which packages are part of the workspace, --filter only matches those packages. In a workspace, --filter can also run scripts in packages located anywhere in the workspace:
terminal
# Packages
# src/foo
# src/bar

# in src/bar: runs myscript in src/foo, no need to cd!
bun run --filter foo myscript

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Parallel and sequential mode

Combine --filter or --workspaces with --parallel or --sequential to run scripts across workspace packages with Foreman-style prefixed output:
terminal
# Run "build" in all matching packages concurrently
bun run --parallel --filter '*' build

# Run "build" in all workspace packages sequentially
bun run --sequential --workspaces build

# Run glob-matched scripts across all packages
bun run --parallel --filter '*' "build:*"

# Continue running even if one package's script fails
bun run --parallel --no-exit-on-error --filter '*' test

# Run multiple scripts across all packages
bun run --parallel --filter '*' build lint
Each line of output is prefixed with the package and script name (pkg-a:build | ...). Without --filter/--workspaces, the prefix is just the script name (build | ...). When a package’s package.json has no name field, Bun uses the relative path from the workspace root instead. Use --if-present with --workspaces to skip packages that don’t have the requested script instead of erroring.

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Dependency Order

Bun respects package dependency order when running scripts. Say you have a package foo that depends on another package bar in your workspace, and both have a build script. When you run bun --filter '*' build, foo only starts once bar is done.