diff --git a/packages/backend/src/misc/cache.ts b/packages/backend/src/misc/cache.ts
index 913258f05a..30a50e5714 100644
--- a/packages/backend/src/misc/cache.ts
+++ b/packages/backend/src/misc/cache.ts
@@ -46,7 +46,7 @@ export class Cache<T> {
 
 		for (const [i, key] of keys.entries()) {
 			const val = values[i];
-			if (val !== null) {
+			if (val != null) {
 				map.set(key, decode(val) as T);
 			}
 		}
diff --git a/packages/backend/src/server/activitypub.ts b/packages/backend/src/server/activitypub.ts
index c9c05adacd..3af3d3c7ac 100644
--- a/packages/backend/src/server/activitypub.ts
+++ b/packages/backend/src/server/activitypub.ts
@@ -127,7 +127,7 @@ router.get("/notes/:note", async (ctx, next) => {
 	}
 
 	// redirect if remote
-	if (note.userHost !== null) {
+	if (note.userHost != null) {
 		if (note.uri == null || isSelfHost(note.userHost)) {
 			ctx.status = 500;
 			return;
diff --git a/packages/backend/src/server/api/endpoints/drive/files/create.ts b/packages/backend/src/server/api/endpoints/drive/files/create.ts
index 54ca5f8d1b..b4a345306b 100644
--- a/packages/backend/src/server/api/endpoints/drive/files/create.ts
+++ b/packages/backend/src/server/api/endpoints/drive/files/create.ts
@@ -82,7 +82,7 @@ export default define(
 	async (ps, user, _, file, cleanup, ip, headers) => {
 		// Get 'name' parameter
 		let name = ps.name || file.originalname;
-		if (name !== undefined && name !== null) {
+		if (name != null) {
 			name = name.trim();
 			if (name.length === 0) {
 				name = null;
diff --git a/packages/backend/src/server/api/endpoints/drive/folders/create.ts b/packages/backend/src/server/api/endpoints/drive/folders/create.ts
index 554e61ec97..5581441980 100644
--- a/packages/backend/src/server/api/endpoints/drive/folders/create.ts
+++ b/packages/backend/src/server/api/endpoints/drive/folders/create.ts
@@ -56,7 +56,7 @@ export default define(meta, paramDef, async (ps, user) => {
 		id: genId(),
 		createdAt: new Date(),
 		name: ps.name,
-		parentId: parent !== null ? parent.id : null,
+		parentId: parent != null ? parent.id : null,
 		userId: user.id,
 	}).then((x) => DriveFolders.findOneByOrFail(x.identifiers[0]));
 
diff --git a/packages/backend/src/server/api/endpoints/drive/folders/update.ts b/packages/backend/src/server/api/endpoints/drive/folders/update.ts
index 5bd880da84..7b266548e5 100644
--- a/packages/backend/src/server/api/endpoints/drive/folders/update.ts
+++ b/packages/backend/src/server/api/endpoints/drive/folders/update.ts
@@ -93,7 +93,7 @@ export default define(meta, paramDef, async (ps, user) => {
 				}
 			}
 
-			if (parent.parentId !== null) {
+			if (parent.parentId != null) {
 				if (await checkCircle(parent.parentId)) {
 					throw new ApiError(meta.errors.recursiveNesting);
 				}
diff --git a/packages/backend/src/server/api/endpoints/notes/edit.ts b/packages/backend/src/server/api/endpoints/notes/edit.ts
index 47143a2658..8e818745fc 100644
--- a/packages/backend/src/server/api/endpoints/notes/edit.ts
+++ b/packages/backend/src/server/api/endpoints/notes/edit.ts
@@ -648,13 +648,13 @@ export default define(meta, paramDef, async (ps, user) => {
 			}
 
 			// Post is a reply and remote user is the contributor of the original post
-			if (note.reply && note.reply.userHost !== null) {
+			if (note.reply?.userHost != null) {
 				const u = await Users.findOneBy({ id: note.reply.userId });
 				if (u && Users.isRemoteUser(u)) dm.addDirectRecipe(u);
 			}
 
 			// Post is a renote and remote user is the contributor of the original post
-			if (note.renote && note.renote.userHost !== null) {
+			if (note.renote?.userHost != null) {
 				const u = await Users.findOneBy({ id: note.renote.userId });
 				if (u && Users.isRemoteUser(u)) dm.addDirectRecipe(u);
 			}
diff --git a/packages/backend/src/server/api/stream/channels/local-timeline.ts b/packages/backend/src/server/api/stream/channels/local-timeline.ts
index 40e38c24f0..3d86d4a10a 100644
--- a/packages/backend/src/server/api/stream/channels/local-timeline.ts
+++ b/packages/backend/src/server/api/stream/channels/local-timeline.ts
@@ -29,7 +29,7 @@ export default class extends Channel {
 	}
 
 	private async onNote(note: Packed<"Note">) {
-		if (note.user.host !== null) return;
+		if (note.user.host != null) return;
 		if (note.visibility !== "public") return;
 		if (note.channelId != null && !this.followingChannels.has(note.channelId))
 			return;
diff --git a/packages/backend/src/services/drive/add-file.ts b/packages/backend/src/services/drive/add-file.ts
index 2f3d3c6e1e..f5dc725577 100644
--- a/packages/backend/src/services/drive/add-file.ts
+++ b/packages/backend/src/services/drive/add-file.ts
@@ -51,14 +51,14 @@ function urlPathJoin(
 				url.pathname.endsWith("/") ? url.pathname.slice(0, -1) : url.pathname,
 			);
 			url.pathname = pathParts
-				.filter((x) => x !== null && x.toString().length > 0)
+				.filter((x) => x != null && x.toString().length > 0)
 				.join("/");
 		}
 		return url.toString();
 	}
 	const baseParts = baseOrParts.concat(pathParts ?? []);
 	return baseParts
-		.filter((x) => x !== null && x.toString().length > 0)
+		.filter((x) => x != null && x.toString().length > 0)
 		.join("/");
 }
 
@@ -614,7 +614,7 @@ export async function addFile({
 	file.createdAt = new Date();
 	file.userId = user ? user.id : null;
 	file.userHost = user ? user.host : null;
-	file.folderId = folder !== null ? folder.id : null;
+	file.folderId = folder != null ? folder.id : null;
 	file.comment = comment;
 	file.properties = properties;
 	file.blurhash = info.blurhash || null;
@@ -626,7 +626,7 @@ export async function addFile({
 	file.isSensitive = user
 		? Users.isLocalUser(user) && profile!.alwaysMarkNsfw
 			? true
-			: sensitive !== null && sensitive !== undefined
+			: sensitive != null
 			? sensitive
 			: false
 		: false;
@@ -635,7 +635,7 @@ export async function addFile({
 	if (info.sensitive && instance.setSensitiveFlagAutomatically)
 		file.isSensitive = true;
 
-	if (url !== null) {
+	if (url != null) {
 		file.src = url;
 
 		if (isLink) {
@@ -647,7 +647,7 @@ export async function addFile({
 		}
 	}
 
-	if (uri !== null) {
+	if (uri != null) {
 		file.uri = uri;
 	}
 
diff --git a/packages/backend/src/services/drive/delete-file.ts b/packages/backend/src/services/drive/delete-file.ts
index 515c1d1c65..2ed01d0e9a 100644
--- a/packages/backend/src/services/drive/delete-file.ts
+++ b/packages/backend/src/services/drive/delete-file.ts
@@ -69,7 +69,7 @@ export async function deleteFileSync(file: DriveFile, isExpired = false) {
 
 async function postProcess(file: DriveFile, isExpired = false) {
 	// リモートファイル期限切れ削除後は直リンクにする
-	if (isExpired && file.userHost !== null && file.uri != null) {
+	if (isExpired && file.userHost != null && file.uri != null) {
 		DriveFiles.update(file.id, {
 			isLink: true,
 			url: file.uri,
@@ -88,7 +88,7 @@ async function postProcess(file: DriveFile, isExpired = false) {
 	// 統計を更新
 	driveChart.update(file, false);
 	perUserDriveChart.update(file, false);
-	if (file.userHost !== null) {
+	if (file.userHost != null) {
 		instanceChart.updateDrive(file, false);
 	}
 }
diff --git a/packages/backend/src/services/drive/upload-from-url.ts b/packages/backend/src/services/drive/upload-from-url.ts
index 0638bcab89..adbeee5a82 100644
--- a/packages/backend/src/services/drive/upload-from-url.ts
+++ b/packages/backend/src/services/drive/upload-from-url.ts
@@ -50,7 +50,7 @@ export async function uploadFromUrl({
 
 	// If the comment is same as the name, skip comment
 	// (image.name is passed in when receiving attachment)
-	if (comment !== null && name === comment) {
+	if (comment != null && name === comment) {
 		comment = null;
 	}
 
diff --git a/packages/backend/src/services/logger.ts b/packages/backend/src/services/logger.ts
index df4c2e3564..ddbebdf30b 100644
--- a/packages/backend/src/services/logger.ts
+++ b/packages/backend/src/services/logger.ts
@@ -115,7 +115,7 @@ export default class Logger {
 
 		console.log(important ? chalk.bold(log) : log);
 
-		if (level === "error" && data !== null) {
+		if (level === "error" && data != null) {
 			console.log(data);
 		}
 
diff --git a/packages/backend/src/services/note/create.ts b/packages/backend/src/services/note/create.ts
index 3a62fce959..6edf5f2ec2 100644
--- a/packages/backend/src/services/note/create.ts
+++ b/packages/backend/src/services/note/create.ts
@@ -490,7 +490,7 @@ export default async (
 				const lock = new Mutex(redisClient, "publishedNote");
 				await lock.acquire();
 				try {
-					const published = (await redisClient.get(publishKey)) !== null;
+					const published = (await redisClient.get(publishKey)) != null;
 					if (!published) {
 						await redisClient.set(publishKey, "done", "EX", 30);
 						if (noteToPublish.renoteId) {
@@ -617,13 +617,13 @@ export default async (
 					}
 
 					// 投稿がリプライかつ投稿者がローカルユーザーかつリプライ先の投稿の投稿者がリモートユーザーなら配送
-					if (data.reply && data.reply.userHost !== null) {
+					if (data.reply?.userHost != null) {
 						const u = await Users.findOneBy({ id: data.reply.userId });
 						if (u && Users.isRemoteUser(u)) dm.addDirectRecipe(u);
 					}
 
 					// 投稿がRenoteかつ投稿者がローカルユーザーかつRenote元の投稿の投稿者がリモートユーザーなら配送
-					if (data.renote && data.renote.userHost !== null) {
+					if (data.renote?.userHost != null) {
 						const u = await Users.findOneBy({ id: data.renote.userId });
 						if (u && Users.isRemoteUser(u)) dm.addDirectRecipe(u);
 					}
diff --git a/packages/backend/src/services/note/reaction/create.ts b/packages/backend/src/services/note/reaction/create.ts
index 123356515d..ac0982dcbe 100644
--- a/packages/backend/src/services/note/reaction/create.ts
+++ b/packages/backend/src/services/note/reaction/create.ts
@@ -151,7 +151,7 @@ export default async (
 	) {
 		const content = renderActivity(await renderLike(record, note));
 		const dm = new DeliverManager(user, content);
-		if (note.userHost !== null) {
+		if (note.userHost != null) {
 			const reactee = await Users.findOneBy({ id: note.userId });
 			dm.addDirectRecipe(reactee as IRemoteUser);
 		}
diff --git a/packages/backend/src/services/note/reaction/delete.ts b/packages/backend/src/services/note/reaction/delete.ts
index 15c6d1cf62..49879a0c02 100644
--- a/packages/backend/src/services/note/reaction/delete.ts
+++ b/packages/backend/src/services/note/reaction/delete.ts
@@ -59,7 +59,7 @@ export default async (
 			renderUndo(await renderLike(reaction, note), user),
 		);
 		const dm = new DeliverManager(user, content);
-		if (note.userHost !== null) {
+		if (note.userHost != null) {
 			const reactee = await Users.findOneBy({ id: note.userId });
 			dm.addDirectRecipe(reactee as IRemoteUser);
 		}