diff --git a/README.md b/README.md
index 1bcb0f9..7d8d049 100644
--- a/README.md
+++ b/README.md
@@ -52,6 +52,12 @@ bounds are too low.
     # (not strict) or 'v0' (strict for "0.*.*" and not strict otherwise).
     # Default: 'v0'
     strict: ''
+
+    # Comma-separated list of Julia projects to modify. The Project.toml files in all of
+    # these directories will be modified.
+    # Example: ., test, docs
+    # Default: .
+    projects: ''
 ```
 
 ## Example
@@ -71,7 +77,7 @@ jobs:
       - uses: julia-actions/julia-downgrade-compat@v1
         if: ${{ matrix.version == '1.6' }}
         with:
-          skip: Pkg,TOML
+          skip: Pkg, TOML
       - uses: julia-actions/julia-buildpkg@v1
       - uses: julia-actions/julia-runtest@v1
 ```
diff --git a/action.yml b/action.yml
index 066ce3e..9fbbb3a 100644
--- a/action.yml
+++ b/action.yml
@@ -7,10 +7,13 @@ inputs:
   strict:
     description: 'true, false or v0. Default: v0.'
     default: 'v0'
+  projects:
+    description: 'Comma-separated list of Julia projects to modify.'
+    default: '.'
 runs:
   using: "composite"
   steps:
-    - run: julia "${{ github.action_path }}/downgrade.jl" "${{ inputs.skip }}" "${{ inputs.strict }}"
+    - run: julia "${{ github.action_path }}/downgrade.jl" "${{ inputs.skip }}" "${{ inputs.strict }}" "${{ inputs.projects }}"
       shell: bash
 branding:
   icon: trending-down
diff --git a/downgrade.jl b/downgrade.jl
index 1057beb..c48d809 100644
--- a/downgrade.jl
+++ b/downgrade.jl
@@ -62,14 +62,18 @@ function downgrade(file, ignore_pkgs, strict)
     end
 end
 
-ignore_pkgs = map(strip, split(ARGS[1], ",", keepempty=false))
+ignore_pkgs = filter(!isempty, map(strip, split(ARGS[1], ",")))
 strict = ARGS[2]
+dirs = filter(!isempty, map(strip, split(ARGS[3], ",")))
 
 strict in ["true", "false", "v0"] || error("strict must be true, false or v0")
 
-project_files = filter(isfile, ["Project.toml", "JuliaProject.toml"])
-isempty(project_files) && error("could not find Project.toml")
-
-for file in project_files
-    downgrade(file, ignore_pkgs, strict)
+for dir in dirs
+    files = [joinpath(dir, "Project.toml"), joinpath(dir, "JuliaProject.toml")]
+    filter!(isfile, files)
+    isempty(files) && error("could not find Project.toml or JuliaProject.toml in $dir")
+    for file in files
+        @info "downgrading $file"
+        downgrade(file, ignore_pkgs, strict)
+    end
 end
diff --git a/test/runtests.jl b/test/runtests.jl
index 463df47..52c7a85 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -5,10 +5,11 @@ downgrade_jl = joinpath(dirname(@__DIR__), "downgrade.jl")
 specs = [
     (
         strict = "v0",
-        ignore = "Pkg0",
+        ignore = "Pkg0, Pkg00",
         compats = [
             ("julia", "1.6", "1.6"),
             ("Pkg0", "1.2", "1.2"),
+            ("Pkg00", "1.3", "1.3"),
             ("Pkg1", "1", "~1.0.0"),
             ("Pkg2", "1.2", "~1.2.0"),
             ("Pkg3", "1.2.3", "~1.2.3"),
@@ -26,10 +27,11 @@ specs = [
     )
     (
         strict = "true",
-        ignore = "Pkg0",
+        ignore = "Pkg0, Pkg00",
         compats = [
             ("julia", "1.6", "1.6"),
             ("Pkg0", "1.2", "1.2"),
+            ("Pkg00", "1.3", "1.3"),
             ("Pkg1", "1", "=1.0.0"),
             ("Pkg2", "1.2", "=1.2.0"),
             ("Pkg3", "1.2.3", "=1.2.3"),
@@ -47,10 +49,11 @@ specs = [
     )
     (
         strict = "false",
-        ignore = "Pkg0",
+        ignore = "Pkg0, Pkg00",
         compats = [
             ("julia", "1.6", "1.6"),
             ("Pkg0", "1.2", "1.2"),
+            ("Pkg00", "1.3", "1.3"),
             ("Pkg1", "1", "~1.0.0"),
             ("Pkg2", "1.2", "~1.2.0"),
             ("Pkg3", "1.2.3", "~1.2.3"),
@@ -85,13 +88,20 @@ function test_downgrade(; strict, ignore, compats, file)
     @info "testing $strict $ignore $file"
     mktempdir() do dir
         cd(dir) do 
-            toml1 = make_toml([(pkg, compat) for (pkg, compat, _) in compats])
-            toml2 = make_toml([(pkg, compat) for (pkg, _, compat) in compats])
-            write("Project.toml", toml1)
-            run(`$(Base.julia_cmd()) $downgrade_jl $ignore $strict`)
-            toml3 = read("Project.toml", String)
-            @test toml3 != toml1
-            @test toml3 == toml2
+            toml1a = make_toml([(pkg, compat) for (pkg, compat, _) in compats])
+            toml2a = make_toml([(pkg, compat) for (pkg, _, compat) in compats])
+            toml1b = toml1a * "# foo\n"
+            toml2b = toml2a * "# foo\n"
+            mkdir("foo")
+            write(file, toml1a)
+            write(joinpath("foo", file), toml1b)
+            run(`$(Base.julia_cmd()) $downgrade_jl $ignore $strict "., foo"`)
+            toml3a = read(file, String)
+            toml3b = read(joinpath("foo", file), String)
+            @test toml3a != toml1a
+            @test toml3a == toml2a
+            @test toml3b != toml1b
+            @test toml3b == toml2b
         end
     end
 end