diff --git a/RelaxVersioner.Core/Processor.cs b/RelaxVersioner.Core/Processor.cs
index 6bb3238..c35bb9a 100644
--- a/RelaxVersioner.Core/Processor.cs
+++ b/RelaxVersioner.Core/Processor.cs
@@ -41,6 +41,7 @@ public sealed class ProcessorContext
     public string BracketStart;
     public string BracketEnd;
     public bool IsDryRun;
+    public string[] NpmPrefixes;
 }
 
 public sealed class Processor
diff --git a/RelaxVersioner.Core/RelaxVersioner.Core.csproj b/RelaxVersioner.Core/RelaxVersioner.Core.csproj
index 6b064d6..38ca466 100644
--- a/RelaxVersioner.Core/RelaxVersioner.Core.csproj
+++ b/RelaxVersioner.Core/RelaxVersioner.Core.csproj
@@ -14,6 +14,7 @@
   <ItemGroup>
     <PackageReference Include="GitReader" Version="1.8.0" />
     <PackageReference Include="NamingFormatter" Version="2.4.0" />
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
     <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.3" PrivateAssets="All" />
     <PackageReference Condition="'$(RV_BOOTSTRAP)' != 'True'"
                       Include="RelaxVersioner" Version="3.7.0" PrivateAssets="all" />
diff --git a/RelaxVersioner.Core/Writers/NpmReplaceProvider.cs b/RelaxVersioner.Core/Writers/NpmReplaceProvider.cs
new file mode 100644
index 0000000..c11e6d8
--- /dev/null
+++ b/RelaxVersioner.Core/Writers/NpmReplaceProvider.cs
@@ -0,0 +1,103 @@
+////////////////////////////////////////////////////////////////////////////////////////
+//
+// RelaxVersioner - Git tag/branch based, full-automatic version generator.
+// Copyright (c) Kouji Matsui (@kozy_kekyo, @kekyo@mastodon.cloud)
+//
+// Licensed under Apache-v2: https://opensource.org/licenses/Apache-2.0
+//
+////////////////////////////////////////////////////////////////////////////////////////
+
+#nullable enable
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Globalization;
+using System.IO;
+using System.Linq;
+using System.Text;
+using NamingFormatter;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+
+namespace RelaxVersioner.Writers;
+
+internal sealed class NpmReplaceProvider : WriteProviderBase
+{
+    public override string Language => "NPM";
+
+    public override void Write(
+        ProcessorContext context,
+        Dictionary<string, object?> keyValues,
+        DateTimeOffset generated)
+    {
+        void Replace(TextReader tr, TextWriter tw)
+        {
+            var jr = new JsonTextReader(tr);
+            var jt = JToken.ReadFrom(jr);
+            
+            var formattedVersion = Named.Format(
+                CultureInfo.InvariantCulture,
+                context.TextFormat,
+                keyValues,
+                key => string.Empty,
+                new(context.BracketStart, context.BracketEnd));
+            
+            jt["version"] = formattedVersion;
+
+            if (context.NpmPrefixes.Length >= 1)
+            {
+                void ReplaceSubKey(string key)
+                {
+                    if (jt[key] is JObject jo)
+                    {
+                        foreach (var jp in jo.Properties())
+                        {
+                            if (context.NpmPrefixes.Any(jp.Name.StartsWith))
+                            {
+                                jp.Value = JValue.CreateString(formattedVersion);
+                            }
+                        }
+                    }
+                }
+            
+                ReplaceSubKey("dependencies");
+                ReplaceSubKey("peerDependencies");
+                ReplaceSubKey("devDependencies");
+            }
+            
+            var jw = new JsonTextWriter(tw);
+            jt.WriteTo(jw);
+
+            jw.Flush();
+            tw.Flush();
+        }
+
+        if (!string.IsNullOrWhiteSpace(context.OutputPath))
+        {
+            if (context.IsDryRun)
+            {
+                return;
+            }
+
+            Processor.WriteSafeTransacted(
+                context.OutputPath,
+                stream =>
+                {
+                    using var tr = context.ReplaceInputPath is { } rip ?
+                        new StreamReader(rip, Encoding.UTF8, true) :
+                        Console.In;
+                    var tw = new StreamWriter(stream, Encoding.UTF8);
+
+                    Replace(tr, tw);
+                });
+        }
+        else
+        {
+            using var tr = context.ReplaceInputPath is { } rip ?
+                new StreamReader(rip, Encoding.UTF8, true) :
+                Console.In;
+            Replace(tr, Console.Out);
+        }
+    }
+}
diff --git a/RelaxVersioner/Program.cs b/RelaxVersioner/Program.cs
index b0e0f7a..df94c50 100644
--- a/RelaxVersioner/Program.cs
+++ b/RelaxVersioner/Program.cs
@@ -33,6 +33,7 @@ public static async Task<int> Main(string[] args)
                 Language = "Text",
                 GenerateStatic = true,
                 TextFormat = "{versionLabel}",
+                NpmPrefixes = Array.Empty<string>(),
             };
 
             string? resultPath = null;
@@ -52,12 +53,7 @@ public static async Task<int> Main(string[] args)
                 { "propertiesPath=", $"properties file", v => context.PropertiesPath = v },
                 { "o|outputPath=", $"output source file", v => context.OutputPath = v },
                 { "resultPath=", $"output result via xml file", v => resultPath = v },
-                { "f|format=", $"set text format", v =>
-                    {
-                         context.TextFormat = v;
-                         context.Language = "Text";
-                    }
-                },
+                { "f|format=", $"set text format", v => context.TextFormat = v },
                 { "r|replace", "replace standard input", _ =>
                     {
                         context.ReplaceInputPath = null;
@@ -79,6 +75,23 @@ public static async Task<int> Main(string[] args)
                         }
                     }
                 },
+                { "n|npm", "replace NPM package.json", v =>
+                    {
+                        context.Language = "NPM";
+                        context.ReplaceInputPath = "package.json";
+                        context.OutputPath = "package.json";
+                        context.TextFormat = "^{versionLabel}";
+                    }
+                },
+                { "npmpn=", "NPM dependency prefix namespaces", v =>
+                    {
+                        context.NpmPrefixes = v.Split(',').Select(n => n.Trim()).ToArray();
+                        context.Language = "NPM";
+                        context.ReplaceInputPath = "package.json";
+                        context.OutputPath = "package.json";
+                        context.TextFormat = "^{versionLabel}";
+                    }
+                },
                 { "dryrun", "dryrun mode", _ => context.IsDryRun = true },
                 { "launchDebugger", "Launch debugger", _ => launchDebugger = true },
                 { "help", "help", v => help = v != null },