diff --git a/__test__/deno_dir_manifest/deps/https/example.com/8611ea80bb4f73e9a0c1207b611d77892ac9a19f840b2d389275e6e4d22c0259 b/__test__/deno_dir_manifest/deps/https/example.com/8611ea80bb4f73e9a0c1207b611d77892ac9a19f840b2d389275e6e4d22c0259
deleted file mode 100644
index 6b8a859..0000000
--- a/__test__/deno_dir_manifest/deps/https/example.com/8611ea80bb4f73e9a0c1207b611d77892ac9a19f840b2d389275e6e4d22c0259
+++ /dev/null
@@ -1 +0,0 @@
-// /demo.json
\ No newline at end of file
diff --git a/__test__/deno_dir_manifest/deps/https/example.com/8611ea80bb4f73e9a0c1207b611d77892ac9a19f840b2d389275e6e4d22c0259.metadata.json b/__test__/deno_dir_manifest/deps/https/example.com/8611ea80bb4f73e9a0c1207b611d77892ac9a19f840b2d389275e6e4d22c0259.metadata.json
deleted file mode 100644
index d6e79cc..0000000
--- a/__test__/deno_dir_manifest/deps/https/example.com/8611ea80bb4f73e9a0c1207b611d77892ac9a19f840b2d389275e6e4d22c0259.metadata.json
+++ /dev/null
@@ -1,4 +0,0 @@
-{
-  "headers": {},
-  "url": "https://example.com/demo.json"
-}
diff --git a/__test__/deno_dir_manifest/deps/https/invalid_meta.com/1d6ab9051e9ae4e3a9d501b1a4316583ae8ecd51d41d327b514abf0194c14dc4 b/__test__/deno_dir_manifest/deps/https/invalid_meta.com/1d6ab9051e9ae4e3a9d501b1a4316583ae8ecd51d41d327b514abf0194c14dc4
new file mode 100644
index 0000000..e69de29
diff --git a/__test__/deno_dir_manifest/deps/https/invalid_meta.com/1d6ab9051e9ae4e3a9d501b1a4316583ae8ecd51d41d327b514abf0194c14dc4.metadata.json b/__test__/deno_dir_manifest/deps/https/invalid_meta.com/1d6ab9051e9ae4e3a9d501b1a4316583ae8ecd51d41d327b514abf0194c14dc4.metadata.json
new file mode 100644
index 0000000..6d4f3ad
--- /dev/null
+++ b/__test__/deno_dir_manifest/deps/https/invalid_meta.com/1d6ab9051e9ae4e3a9d501b1a4316583ae8ecd51d41d327b514abf0194c14dc4.metadata.json
@@ -0,0 +1,5 @@
+{
+  "headers": {
+    "missing-url": true
+  }
+}
diff --git a/__test__/deno_dir_manifest/deps/https/invalid_meta.com/2f5c120425d2222c81506ea48f25c608a89272ed179233ab4fd47debb0f5d05f b/__test__/deno_dir_manifest/deps/https/invalid_meta.com/2f5c120425d2222c81506ea48f25c608a89272ed179233ab4fd47debb0f5d05f
new file mode 100644
index 0000000..e69de29
diff --git a/__test__/deno_dir_manifest/deps/https/invalid_meta.com/2f5c120425d2222c81506ea48f25c608a89272ed179233ab4fd47debb0f5d05f.metadata.json b/__test__/deno_dir_manifest/deps/https/invalid_meta.com/2f5c120425d2222c81506ea48f25c608a89272ed179233ab4fd47debb0f5d05f.metadata.json
new file mode 100644
index 0000000..ec4c24c
--- /dev/null
+++ b/__test__/deno_dir_manifest/deps/https/invalid_meta.com/2f5c120425d2222c81506ea48f25c608a89272ed179233ab4fd47debb0f5d05f.metadata.json
@@ -0,0 +1,3 @@
+{
+  "url": "https://invalid_meta.com/missing_headers"
+}
diff --git a/__test__/deno_dir_manifest/deps/https/unknown_module.com/27e936010957fa71c39ae46b56a40b4b4c5b388f50d950637e4522708a340663 b/__test__/deno_dir_manifest/deps/https/unknown_module.com/27e936010957fa71c39ae46b56a40b4b4c5b388f50d950637e4522708a340663
new file mode 100644
index 0000000..e69de29
diff --git a/__test__/deno_dir_manifest/deps/https/unknown_module.com/27e936010957fa71c39ae46b56a40b4b4c5b388f50d950637e4522708a340663.metadata.json b/__test__/deno_dir_manifest/deps/https/unknown_module.com/27e936010957fa71c39ae46b56a40b4b4c5b388f50d950637e4522708a340663.metadata.json
new file mode 100644
index 0000000..ed8023d
--- /dev/null
+++ b/__test__/deno_dir_manifest/deps/https/unknown_module.com/27e936010957fa71c39ae46b56a40b4b4c5b388f50d950637e4522708a340663.metadata.json
@@ -0,0 +1,4 @@
+{
+  "headers": {},
+  "url": "https://unknown_module.com/unknown_module_without_extension"
+}
diff --git a/core/extension.test.ts b/core/extension.test.ts
index f7c16be..00e7020 100644
--- a/core/extension.test.ts
+++ b/core/extension.test.ts
@@ -1,4 +1,4 @@
-import { getExtensionFromFile } from "./extension";
+import { getExtensionFromFile, isValidDenoModuleExtension } from "./extension";
 
 test("core / extension: getExtensionFromFile", async () => {
   expect(getExtensionFromFile("./foo.ts")).toBe(".ts");
@@ -6,7 +6,17 @@ test("core / extension: getExtensionFromFile", async () => {
   expect(getExtensionFromFile("./foo.js")).toBe(".js");
   expect(getExtensionFromFile("./foo.jsx")).toBe(".jsx");
   expect(getExtensionFromFile("./foo.d.ts")).toBe(".d.ts");
-  expect(getExtensionFromFile("./foo.json")).toBe(".json");
   expect(getExtensionFromFile("./foo.wasm")).toBe(".wasm");
   expect(getExtensionFromFile("./foo")).toBe("");
 });
+
+test("core / extension: isValidDenoModuleExtension", async () => {
+  expect(isValidDenoModuleExtension("./foo.ts")).toBeTruthy();
+  expect(isValidDenoModuleExtension("./foo.tsx")).toBeTruthy();
+  expect(isValidDenoModuleExtension("./foo.js")).toBeTruthy();
+  expect(isValidDenoModuleExtension("./foo.jsx")).toBeTruthy();
+  expect(isValidDenoModuleExtension("./foo.d.ts")).toBeTruthy();
+  expect(isValidDenoModuleExtension("./foo.wasm")).toBeTruthy();
+  expect(isValidDenoModuleExtension("./foo")).toBeFalsy();
+  expect(isValidDenoModuleExtension("./foo.json")).toBeFalsy();
+});
diff --git a/core/extension.ts b/core/extension.ts
index 6bf4949..30bdb12 100644
--- a/core/extension.ts
+++ b/core/extension.ts
@@ -6,7 +6,6 @@ export type Extension =
   | ".d.ts"
   | ".js"
   | ".jsx"
-  | ".json"
   | ".wasm"
   | "";
 
@@ -21,3 +20,11 @@ export function getExtensionFromFile(filename: string): Extension {
 
   return extName as Extension;
 }
+
+export function isValidDenoModuleExtension(filename: string): boolean {
+  if (/\.(tsx?|jsx?|d\.ts|wasm)$/.test(filename)) {
+    return true;
+  }
+
+  return false;
+}
diff --git a/core/hash_meta.test.ts b/core/hash_meta.test.ts
index 66fc632..9fb5757 100644
--- a/core/hash_meta.test.ts
+++ b/core/hash_meta.test.ts
@@ -48,24 +48,6 @@ test("core / hash_meta with javascript file", () => {
   expect(meta.destinationFilepath).toEqual(cacheFilepath);
 });
 
-test("core / hash_meta with json file", () => {
-  const cacheFilepath = path.join(
-    denoDir,
-    "deps",
-    "https",
-    "example.com",
-    "8611ea80bb4f73e9a0c1207b611d77892ac9a19f840b2d389275e6e4d22c0259"
-  );
-
-  const meta = HashMeta.create(cacheFilepath + ".metadata.json") as HashMeta;
-  expect(meta).not.toBe(undefined);
-  expect(meta.filepath).toEqual(cacheFilepath + ".metadata.json");
-  expect(meta.type).toEqual(Type.JSON);
-  expect(meta.extension).toEqual(".json");
-  expect(meta.url.href).toEqual("https://example.com/demo.json");
-  expect(meta.destinationFilepath).toEqual(cacheFilepath);
-});
-
 test("core / hash_meta without extension name", () => {
   const cacheFilepath = path.join(
     denoDir,
@@ -132,3 +114,29 @@ test("core / hash_meta: if not exist", () => {
   const meta = HashMeta.create(notExistCache + ".metadata.json");
   expect(meta).toBe(undefined);
 });
+
+test("core / hash_meta: if meta file missing url", () => {
+  const notExistCache = path.join(
+    denoDir,
+    "deps",
+    "https",
+    "invalid_mta.com",
+    "1d6ab9051e9ae4e3a9d501b1a4316583ae8ecd51d41d327b514abf0194c14dc4"
+  );
+
+  const meta = HashMeta.create(notExistCache + ".metadata.json");
+  expect(meta).toBe(undefined);
+});
+
+test("core / hash_meta: if meta file missing headers", () => {
+  const notExistCache = path.join(
+    denoDir,
+    "deps",
+    "https",
+    "invalid_mta.com",
+    "2f5c120425d2222c81506ea48f25c608a89272ed179233ab4fd47debb0f5d05f"
+  );
+
+  const meta = HashMeta.create(notExistCache + ".metadata.json");
+  expect(meta).toBe(undefined);
+});
diff --git a/core/hash_meta.ts b/core/hash_meta.ts
index 2cbf553..555bee1 100644
--- a/core/hash_meta.ts
+++ b/core/hash_meta.ts
@@ -16,7 +16,6 @@ export enum Type {
   JavaScriptReact = "javascriptreact",
   TypeScript = "typescript",
   TypeScriptReact = "typescriptreact",
-  JSON = "json",
   WebAssembly = "WebAssembly",
   PlainText = "plaintext",
 }
@@ -35,7 +34,6 @@ const extNameMap: { [key: string]: Type } = {
   ".js": Type.JavaScript,
   ".jsx": Type.JavaScriptReact,
   ".mjs": Type.JavaScript,
-  ".json": Type.JSON,
   ".wasm": Type.WebAssembly,
 };
 
@@ -55,7 +53,6 @@ const contentTypeMap: [string[], Type][] = [
     ],
     Type.JavaScript,
   ],
-  [["application/json"], Type.JSON],
   [["application/wasm"], Type.WebAssembly],
 ];
 
@@ -69,6 +66,10 @@ export class HashMeta implements HashMetaInterface {
       fs.readFileSync(metaFilepath, { encoding: "utf8" })
     );
 
+    if (!metaMap.url || !metaMap.headers) {
+      return;
+    }
+
     return new HashMeta(metaFilepath, new URL(metaMap.url), metaMap.headers);
   }
   private constructor(
@@ -117,8 +118,6 @@ export class HashMeta implements HashMetaInterface {
       /* istanbul ignore next */
       case Type.TypeScriptReact:
         return ".tsx";
-      case Type.JSON:
-        return ".json";
       /* istanbul ignore next */
       case Type.WebAssembly:
         return ".wasm";
diff --git a/core/module_resolver.test.ts b/core/module_resolver.test.ts
index e385b9d..76f6ba5 100644
--- a/core/module_resolver.test.ts
+++ b/core/module_resolver.test.ts
@@ -79,6 +79,7 @@ test("core / module_resolver: resolve module from local", () => {
       `file://${path.join(__dirname, "cache.ts")}`,
       `file://./cache.ts`,
       `file://../client/src/extension.ts`,
+      `https://unknown_module.com/unknown_module_without_extension`,
     ])
   ).toEqual([
     {
@@ -86,11 +87,7 @@ test("core / module_resolver: resolve module from local", () => {
       origin: "./deno.ts",
       filepath: path.join(__dirname, "deno.ts"),
     },
-    {
-      extension: ".json",
-      origin: "../package.json",
-      filepath: path.join(__dirname, "..", "package.json"),
-    },
+    undefined,
     {
       extension: ".ts",
       origin: "https://example.com/esm/mod.ts",
@@ -146,6 +143,7 @@ test("core / module_resolver: resolve module from local", () => {
       origin: "file://../client/src/extension.ts",
       filepath: path.join(__dirname, "..", "client", "src", "extension.ts"),
     },
+    undefined,
   ] as ResolvedModule[]);
 });
 
diff --git a/core/module_resolver.ts b/core/module_resolver.ts
index 7129184..ce40ca9 100644
--- a/core/module_resolver.ts
+++ b/core/module_resolver.ts
@@ -8,7 +8,11 @@ import { ImportMap } from "./import_map";
 import { HashMeta } from "./hash_meta";
 import { pathExistsSync, isHttpURL, hashURL, normalizeFilepath } from "./util";
 import { Logger } from "./logger";
-import { Extension, getExtensionFromFile } from "./extension";
+import {
+  Extension,
+  getExtensionFromFile,
+  isValidDenoModuleExtension,
+} from "./extension";
 
 export type ResolvedModule = {
   origin: string;
@@ -121,6 +125,10 @@ export class ModuleResolver implements ModuleResolverInterface {
       }
     }
 
+    if (!meta.extension) {
+      return;
+    }
+
     return {
       origin: origin,
       filepath: moduleFilepath,
@@ -149,7 +157,10 @@ export class ModuleResolver implements ModuleResolverInterface {
       normalizeFilepath(moduleName)
     );
 
-    if (!pathExistsSync(moduleFilepath)) {
+    if (
+      !pathExistsSync(moduleFilepath) ||
+      !isValidDenoModuleExtension(moduleFilepath)
+    ) {
       return;
     }