diff --git a/packages/backend/src/boot/master.ts b/packages/backend/src/boot/master.ts
index 1093e6edc..8583823ee 100644
--- a/packages/backend/src/boot/master.ts
+++ b/packages/backend/src/boot/master.ts
@@ -110,13 +110,12 @@ function loadConfigBoot(): Config {
 	try {
 		config = loadConfig();
 	} catch (exception) {
-		if (typeof exception === 'string') {
-			configLogger.error(exception);
-			process.exit(1);
-		}
 		if (exception.code === 'ENOENT') {
 			configLogger.error('Configuration file not found', null, true);
 			process.exit(1);
+		} else if (e instanceof Error) {
+			configLogger.error(e.message);
+			process.exit(1);
 		}
 		throw exception;
 	}
diff --git a/packages/backend/src/config/load.ts b/packages/backend/src/config/load.ts
index d82c8a396..535f258df 100644
--- a/packages/backend/src/config/load.ts
+++ b/packages/backend/src/config/load.ts
@@ -59,6 +59,6 @@ function tryCreateUrl(url: string) {
 	try {
 		return new URL(url);
 	} catch (e) {
-		throw `url="${url}" is not a valid URL.`;
+		throw new Error(`url="${url}" is not a valid URL.`);
 	}
 }
diff --git a/packages/backend/src/misc/captcha.ts b/packages/backend/src/misc/captcha.ts
index 2a128c25f..4238116fe 100644
--- a/packages/backend/src/misc/captcha.ts
+++ b/packages/backend/src/misc/captcha.ts
@@ -5,23 +5,23 @@ import { getAgentByUrl } from './fetch.js';
 
 export async function verifyRecaptcha(secret: string, response: string) {
 	const result = await getCaptchaResponse('https://www.recaptcha.net/recaptcha/api/siteverify', secret, response).catch(e => {
-		throw `recaptcha-request-failed: ${e}`;
+		throw new Error(`recaptcha-request-failed: ${e.message}`);
 	});
 
 	if (result.success !== true) {
 		const errorCodes = result['error-codes'] ? result['error-codes']?.join(', ') : '';
-		throw `recaptcha-failed: ${errorCodes}`;
+		throw new Error(`recaptcha-failed: ${errorCodes}`);
 	}
 }
 
 export async function verifyHcaptcha(secret: string, response: string) {
 	const result = await getCaptchaResponse('https://hcaptcha.com/siteverify', secret, response).catch(e => {
-		throw `hcaptcha-request-failed: ${e}`;
+		throw new Error(`hcaptcha-request-failed: ${e.message}`);
 	});
 
 	if (result.success !== true) {
 		const errorCodes = result['error-codes'] ? result['error-codes']?.join(', ') : '';
-		throw `hcaptcha-failed: ${errorCodes}`;
+		throw new Error(`hcaptcha-failed: ${errorCodes}`);
 	}
 }
 
@@ -46,11 +46,11 @@ async function getCaptchaResponse(url: string, secret: string, response: string)
 		//timeout: 10 * 1000,
 		agent: getAgentByUrl,
 	}).catch(e => {
-		throw `${e.message || e}`;
+		throw new Error(`${e.message || e}`);
 	});
 
 	if (!res.ok) {
-		throw `${res.status}`;
+		throw new Error(`${res.status}`);
 	}
 
 	return await res.json() as CaptchaResponse;
diff --git a/packages/backend/src/misc/gen-id.ts b/packages/backend/src/misc/gen-id.ts
index 1a7a511b6..3caa81906 100644
--- a/packages/backend/src/misc/gen-id.ts
+++ b/packages/backend/src/misc/gen-id.ts
@@ -13,7 +13,7 @@ export function genId(date?: Date): string {
 	let t = date.getTime();
 	t -= TIME2000;
 	if (t < 0) t = 0;
-	if (isNaN(t)) throw 'Failed to create AID: Invalid Date';
+	if (isNaN(t)) throw new Error('Failed to create AID: Invalid Date');
 	const time = t.toString(36).padStart(8, '0');
 
 	counter++;
diff --git a/packages/backend/src/prelude/time.ts b/packages/backend/src/prelude/time.ts
index 34e8b6b17..0da1f7913 100644
--- a/packages/backend/src/prelude/time.ts
+++ b/packages/backend/src/prelude/time.ts
@@ -13,7 +13,7 @@ export function dateUTC(time: number[]): Date {
 					: time.length === 7 ? Date.UTC(time[0], time[1], time[2], time[3], time[4], time[5], time[6])
 					: null;
 
-	if (!d) throw 'wrong number of arguments';
+	if (!d) throw new Error('wrong number of arguments');
 
 	return new Date(d);
 }
diff --git a/packages/backend/src/queue/processors/db/import-blocking.ts b/packages/backend/src/queue/processors/db/import-blocking.ts
index ec6061aba..33bf45730 100644
--- a/packages/backend/src/queue/processors/db/import-blocking.ts
+++ b/packages/backend/src/queue/processors/db/import-blocking.ts
@@ -55,7 +55,7 @@ export async function importBlocking(job: Bull.Job<DbUserImportJobData>, done: a
 			}
 
 			if (target == null) {
-				throw `cannot resolve user: @${username}@${host}`;
+				throw new Error(`cannot resolve user: @${username}@${host}`);
 			}
 
 			// skip myself
diff --git a/packages/backend/src/queue/processors/db/import-following.ts b/packages/backend/src/queue/processors/db/import-following.ts
index a19612389..e01ffe517 100644
--- a/packages/backend/src/queue/processors/db/import-following.ts
+++ b/packages/backend/src/queue/processors/db/import-following.ts
@@ -55,7 +55,7 @@ export async function importFollowing(job: Bull.Job<DbUserImportJobData>, done:
 			}
 
 			if (target == null) {
-				throw `cannot resolve user: @${username}@${host}`;
+				throw new Error(`cannot resolve user: @${username}@${host}`);
 			}
 
 			// skip myself
diff --git a/packages/backend/src/queue/processors/db/import-muting.ts b/packages/backend/src/queue/processors/db/import-muting.ts
index b0c69829b..ec7c6a8d7 100644
--- a/packages/backend/src/queue/processors/db/import-muting.ts
+++ b/packages/backend/src/queue/processors/db/import-muting.ts
@@ -56,7 +56,7 @@ export async function importMuting(job: Bull.Job<DbUserImportJobData>, done: any
 			}
 
 			if (target == null) {
-				throw `cannot resolve user: @${username}@${host}`;
+				throw new Error(`cannot resolve user: @${username}@${host}`);
 			}
 
 			// skip myself
diff --git a/packages/backend/src/queue/processors/deliver.ts b/packages/backend/src/queue/processors/deliver.ts
index a9229a4bc..a7a0e4be9 100644
--- a/packages/backend/src/queue/processors/deliver.ts
+++ b/packages/backend/src/queue/processors/deliver.ts
@@ -89,7 +89,7 @@ export default async (job: Bull.Job<DeliverJobData>) => {
 			}
 
 			// 5xx etc.
-			throw `${res.statusCode} ${res.statusMessage}`;
+			throw new Error(`${res.statusCode} ${res.statusMessage}`);
 		} else {
 			// DNS error, socket error, timeout ...
 			throw res;
diff --git a/packages/backend/src/queue/processors/inbox.ts b/packages/backend/src/queue/processors/inbox.ts
index f48c5e266..bf25aca20 100644
--- a/packages/backend/src/queue/processors/inbox.ts
+++ b/packages/backend/src/queue/processors/inbox.ts
@@ -62,7 +62,7 @@ export default async (job: Bull.Job<InboxJobData>): Promise<string> => {
 				if (e.isClientError) {
 					return `skip: Ignored deleted actors on both ends ${activity.actor} - ${e.statusCode}`;
 				}
-				throw `Error in actor ${activity.actor} - ${e.statusCode || e}`;
+				throw new Error(`Error in actor ${activity.actor} - ${e.statusCode || e}`);
 			}
 		}
 	}
diff --git a/packages/backend/src/queue/processors/webhook-deliver.ts b/packages/backend/src/queue/processors/webhook-deliver.ts
index 64396b458..07dfb61c6 100644
--- a/packages/backend/src/queue/processors/webhook-deliver.ts
+++ b/packages/backend/src/queue/processors/webhook-deliver.ts
@@ -49,7 +49,7 @@ export default async (job: Bull.Job<WebhookDeliverJobData>) => {
 			}
 
 			// 5xx etc.
-			throw `${res.statusCode} ${res.statusMessage}`;
+			throw new Error(`${res.statusCode} ${res.statusMessage}`);
 		} else {
 			// DNS error, socket error, timeout ...
 			throw res;
diff --git a/packages/backend/src/remote/activitypub/misc/ld-signature.ts b/packages/backend/src/remote/activitypub/misc/ld-signature.ts
index 49a8dbbe9..4e0940a72 100644
--- a/packages/backend/src/remote/activitypub/misc/ld-signature.ts
+++ b/packages/backend/src/remote/activitypub/misc/ld-signature.ts
@@ -85,7 +85,7 @@ export class LdSignature {
 
 	private getLoader() {
 		return async (url: string): Promise<any> => {
-			if (!url.match('^https?\:\/\/')) throw `Invalid URL ${url}`;
+			if (!url.match('^https?\:\/\/')) throw new Error(`Invalid URL ${url}`);
 
 			if (this.preLoad) {
 				if (url in CONTEXTS) {
@@ -118,7 +118,7 @@ export class LdSignature {
 			agent: u => u.protocol === 'http:' ? httpAgent : httpsAgent,
 		}).then(res => {
 			if (!res.ok) {
-				throw `${res.status} ${res.statusText}`;
+				throw new Error(`${res.status} ${res.statusText}`);
 			} else {
 				return res.json();
 			}
diff --git a/packages/backend/src/remote/activitypub/models/note.ts b/packages/backend/src/remote/activitypub/models/note.ts
index b1fa1a0cb..c532f81ae 100644
--- a/packages/backend/src/remote/activitypub/models/note.ts
+++ b/packages/backend/src/remote/activitypub/models/note.ts
@@ -189,7 +189,7 @@ export async function createNote(value: string | IObject, resolver?: Resolver, s
 		quote = results.filter((x): x is { status: 'ok', res: Note | null } => x.status === 'ok').map(x => x.res).find(x => x);
 		if (!quote) {
 			if (results.some(x => x.status === 'temperror')) {
-				throw 'quote resolve failed';
+				throw new Error('quote resolve failed');
 			}
 		}
 	}
@@ -276,7 +276,7 @@ export async function resolveNote(value: string | IObject, resolver?: Resolver):
 
 	// ブロックしてたら中断
 	const meta = await fetchMeta();
-	if (meta.blockedHosts.includes(extractDbHost(uri))) throw { statusCode: 451 };
+	if (meta.blockedHosts.includes(extractDbHost(uri))) throw new StatusError('host blocked', 451, `host ${extractDbHost(uri)} is blocked`);
 
 	const unlock = await getApLock(uri);
 
diff --git a/packages/backend/src/server/api/endpoints/admin/relays/add.ts b/packages/backend/src/server/api/endpoints/admin/relays/add.ts
index caee34787..94f757bdc 100644
--- a/packages/backend/src/server/api/endpoints/admin/relays/add.ts
+++ b/packages/backend/src/server/api/endpoints/admin/relays/add.ts
@@ -27,6 +27,7 @@ export const meta = {
 				format: 'id',
 			},
 			inbox: {
+				description: 'URL of the inbox, must be a https scheme URL',
 				type: 'string',
 				optional: false, nullable: false,
 				format: 'url',
@@ -56,7 +57,7 @@ export const paramDef = {
 // eslint-disable-next-line import/no-default-export
 export default define(meta, paramDef, async (ps, user) => {
 	try {
-		if (new URL(ps.inbox).protocol !== 'https:') throw 'https only';
+		if (new URL(ps.inbox).protocol !== 'https:') throw new Error('https only');
 	} catch {
 		throw new ApiError(meta.errors.invalidUrl);
 	}
diff --git a/packages/backend/src/server/api/endpoints/admin/suspend-user.ts b/packages/backend/src/server/api/endpoints/admin/suspend-user.ts
index 8b62daf7a..90ad703a3 100644
--- a/packages/backend/src/server/api/endpoints/admin/suspend-user.ts
+++ b/packages/backend/src/server/api/endpoints/admin/suspend-user.ts
@@ -68,7 +68,7 @@ async function unFollowAll(follower: User) {
 		});
 
 		if (followee == null) {
-			throw `Cant find followee ${following.followeeId}`;
+			throw new Error(`Cant find followee ${following.followeeId}`);
 		}
 
 		await deleteFollowing(follower, followee, true);
diff --git a/packages/backend/src/server/api/endpoints/notes/search-by-tag.ts b/packages/backend/src/server/api/endpoints/notes/search-by-tag.ts
index 777de7221..ef9f6c39c 100644
--- a/packages/backend/src/server/api/endpoints/notes/search-by-tag.ts
+++ b/packages/backend/src/server/api/endpoints/notes/search-by-tag.ts
@@ -86,14 +86,14 @@ export default define(meta, paramDef, async (ps, me) => {
 
 	try {
 		if (ps.tag) {
-			if (!safeForSql(ps.tag)) throw 'Injection';
+			if (!safeForSql(ps.tag)) throw new Error('Injection');
 			query.andWhere(`'{"${normalizeForSearch(ps.tag)}"}' <@ note.tags`);
 		} else {
 			query.andWhere(new Brackets(qb => {
 				for (const tags of ps.query!) {
 					qb.orWhere(new Brackets(qb => {
 						for (const tag of tags) {
-							if (!safeForSql(tag)) throw 'Injection';
+							if (!safeForSql(tag)) throw new Error('Injection');
 							qb.andWhere(`'{"${normalizeForSearch(tag)}"}' <@ note.tags`);
 						}
 					}));
@@ -101,7 +101,7 @@ export default define(meta, paramDef, async (ps, me) => {
 			}));
 		}
 	} catch (e) {
-		if (e === 'Injection') return [];
+		if (e.message === 'Injection') return [];
 		throw e;
 	}
 
diff --git a/packages/backend/src/server/api/endpoints/reset-db.ts b/packages/backend/src/server/api/endpoints/reset-db.ts
index 02adfb540..7f17339e9 100644
--- a/packages/backend/src/server/api/endpoints/reset-db.ts
+++ b/packages/backend/src/server/api/endpoints/reset-db.ts
@@ -21,7 +21,7 @@ export const paramDef = {
 
 // eslint-disable-next-line import/no-default-export
 export default define(meta, paramDef, async (ps, user) => {
-	if (process.env.NODE_ENV !== 'test') throw 'NODE_ENV is not a test';
+	if (process.env.NODE_ENV !== 'test') throw new Error('NODE_ENV is not a test');
 
 	await resetDb();
 
diff --git a/packages/backend/src/services/fetch-instance-metadata.ts b/packages/backend/src/services/fetch-instance-metadata.ts
index cd8cc7f33..d318ed74c 100644
--- a/packages/backend/src/services/fetch-instance-metadata.ts
+++ b/packages/backend/src/services/fetch-instance-metadata.ts
@@ -94,14 +94,14 @@ async function fetchNodeinfo(instance: Instance): Promise<NodeInfo> {
 		const wellknown = await getJson('https://' + instance.host + '/.well-known/nodeinfo')
 			.catch(e => {
 				if (e.statusCode === 404) {
-					throw 'No nodeinfo provided';
+					throw new Error('No nodeinfo provided');
 				} else {
-					throw e.statusCode || e.message;
+					throw new Error(e.statusCode || e.message);
 				}
 			}) as Record<string, unknown>;
 
 		if (wellknown.links == null || !Array.isArray(wellknown.links)) {
-			throw 'No wellknown links';
+			throw new Error('No wellknown links');
 		}
 
 		const links = wellknown.links as any[];
@@ -112,19 +112,19 @@ async function fetchNodeinfo(instance: Instance): Promise<NodeInfo> {
 		const link = lnik2_1 || lnik2_0 || lnik1_0;
 
 		if (link == null) {
-			throw 'No nodeinfo link provided';
+			throw new Error('No nodeinfo link provided');
 		}
 
 		const info = await getJson(link.href)
 			.catch(e => {
-				throw e.statusCode || e.message;
+				throw new Error(e.statusCode || e.message);
 			});
 
 		logger.succ(`Successfuly fetched nodeinfo of ${instance.host}`);
 
 		return info as NodeInfo;
 	} catch (e) {
-		logger.error(`Failed to fetch nodeinfo of ${instance.host}: ${e}`);
+		logger.error(`Failed to fetch nodeinfo of ${instance.host}: ${e.message}`);
 
 		throw e;
 	}
diff --git a/packages/backend/src/services/relay.ts b/packages/backend/src/services/relay.ts
index 6bc430443..a05645f09 100644
--- a/packages/backend/src/services/relay.ts
+++ b/packages/backend/src/services/relay.ts
@@ -47,7 +47,7 @@ export async function removeRelay(inbox: string) {
 	});
 
 	if (relay == null) {
-		throw 'relay not found';
+		throw new Error('relay not found');
 	}
 
 	const relayActor = await getRelayActor();