diff --git a/ArcFormats/ArcASAR.cs b/ArcFormats/ArcASAR.cs
new file mode 100644
index 00000000..824491fe
--- /dev/null
+++ b/ArcFormats/ArcASAR.cs
@@ -0,0 +1,92 @@
+//! \file       ArcASAR.cs
+//! \date       2025-12-23
+//! \brief      Electron/Atom Shell resource archive format.
+//
+// Copyright (C) 2025 by morkt
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to
+// deal in the Software without restriction, including without limitation the
+// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+// sell copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+// IN THE SOFTWARE.
+//
+
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.Composition;
+using System.Text;
+using Newtonsoft.Json;
+
+namespace GameRes.Formats.Chromium
+{
+    class AsarNode
+    {
+        [JsonProperty("files")]
+        public Dictionary<string, AsarNode> Files { get; set; }
+
+        [JsonProperty("size")]
+        public uint Size { get; set; }
+
+        [JsonProperty("offset")]
+        public string Offset { get; set; }
+    }
+
+    [Export(typeof(ArchiveFormat))]
+    public class AsarOpener : ArchiveFormat
+    {
+        public override string         Tag { get { return "ASAR"; } }
+        public override string Description { get { return "Electron/Atom Shell archive format"; } }
+        public override uint     Signature { get { return 0; } }
+        public override bool  IsHierarchic { get { return true; } }
+        public override bool      CanWrite { get { return false; } }
+
+        public AsarOpener ()
+        {
+            Extensions = new string[] { "asar" };
+        }
+
+        public override ArcFile TryOpen (ArcView file)
+        {
+            uint index_size = file.View.ReadUInt32 (0x0C);
+            string json = file.View.ReadString (0x10, index_size, Encoding.UTF8);
+            var dict = JsonConvert.DeserializeObject<AsarNode> (json);
+            var dir = new List<Entry> ();
+            ParseIndex (dir, dict, (uint)((index_size + 0x10 + 3) & ~3));
+            return new ArcFile (file, this, dir);
+        }
+
+        internal void ParseIndex (List<Entry> dir, AsarNode dict, uint pad, string cur = "") {
+            if (dict.Files != null)
+            {
+                foreach (var kv in dict.Files)
+                {
+                    string k = kv.Key;
+                    AsarNode v = kv.Value;
+                    ParseIndex (dir, v, pad, cur != "" ? $"{cur}/{k}" : k);
+                }
+            }
+            else
+            {
+                var entry = new Entry {
+                    Name = cur,
+                    Size = dict.Size,
+                    Offset = uint.Parse (dict.Offset) + pad,
+                    Type = FormatCatalog.Instance.GetTypeFromName (cur)
+                };
+                dir.Add (entry);
+            }
+        }
+    }
+}
diff --git a/ArcFormats/ArcFormats.csproj b/ArcFormats/ArcFormats.csproj
index 51dee7e9..8df6b724 100644
--- a/ArcFormats/ArcFormats.csproj
+++ b/ArcFormats/ArcFormats.csproj
@@ -63,6 +63,9 @@
     <Reference Include="NVorbis, Version=0.10.4.0, Culture=neutral, processorArchitecture=MSIL">
       <HintPath>..\packages\NVorbis.0.10.4\lib\net45\NVorbis.dll</HintPath>
     </Reference>
+    <Reference Include="Newtonsoft.Json, Version=13.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed, processorArchitecture=MSIL">
+      <HintPath>..\packages\Newtonsoft.Json.13.0.3\lib\net45\Newtonsoft.Json.dll</HintPath>
+    </Reference>
     <Reference Include="PresentationCore" />
     <Reference Include="PresentationFramework" />
     <Reference Include="Snappy.NET, Version=1.1.1.8, Culture=neutral, processorArchitecture=MSIL">
@@ -194,6 +197,7 @@
     <Compile Include="Aoi\ImageAGF.cs" />
     <Compile Include="Apricot\ArcDAT.cs" />
     <Compile Include="ArcARCX.cs" />
+    <Compile Include="ArcASAR.cs" />
     <Compile Include="Artemis\ArcMJA.cs" />
     <Compile Include="Macintosh\ImagePICT.cs" />
     <Compile Include="Macromedia\ArcDXR.cs" />
diff --git a/ArcFormats/packages.config b/ArcFormats/packages.config
index 9b9f1981..74a50b67 100644
--- a/ArcFormats/packages.config
+++ b/ArcFormats/packages.config
@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
   <package id="Crc32C.NET" version="1.0.5.0" targetFramework="net461" />
+  <package id="Newtonsoft.Json" version="13.0.3" targetFramework="net461" />
   <package id="NVorbis" version="0.10.4" targetFramework="net461" />
   <package id="SharpZipLib" version="1.3.3" targetFramework="net461" />
   <package id="Snappy.NET" version="1.1.1.8" targetFramework="net461" />