diff --git a/src/client/__tests__/csrf.test.js b/src/client/__tests__/csrf.test.js
index 7a7562529e..134c285489 100644
--- a/src/client/__tests__/csrf.test.js
+++ b/src/client/__tests__/csrf.test.js
@@ -78,11 +78,10 @@ test("when the fetch fails it'll throw a client fetch error", async () => {
 
   await waitFor(() => {
     expect(logger.error).toHaveBeenCalledTimes(1)
-    expect(logger.error).toBeCalledWith(
-      "CLIENT_FETCH_ERROR",
-      "csrf",
-      new SyntaxError("Unexpected token s in JSON at position 0")
-    )
+    expect(logger.error).toBeCalledWith("CLIENT_FETCH_ERROR", {
+      path: "csrf",
+      error: new SyntaxError("Unexpected token s in JSON at position 0"),
+    })
   })
 })
 
diff --git a/src/client/__tests__/providers.test.js b/src/client/__tests__/providers.test.js
index acf9f2045f..3a7476814e 100644
--- a/src/client/__tests__/providers.test.js
+++ b/src/client/__tests__/providers.test.js
@@ -56,11 +56,10 @@ test("when failing to fetch the providers, it'll log the error", async () => {
 
   await waitFor(() => {
     expect(logger.error).toHaveBeenCalledTimes(1)
-    expect(logger.error).toBeCalledWith(
-      "CLIENT_FETCH_ERROR",
-      "providers",
-      new SyntaxError("Unexpected token s in JSON at position 0")
-    )
+    expect(logger.error).toBeCalledWith("CLIENT_FETCH_ERROR", {
+      path: "providers",
+      error: new SyntaxError("Unexpected token s in JSON at position 0"),
+    })
   })
 })
 
diff --git a/src/client/__tests__/session.test.js b/src/client/__tests__/session.test.js
index 983c3f85ea..82e27b1dbe 100644
--- a/src/client/__tests__/session.test.js
+++ b/src/client/__tests__/session.test.js
@@ -70,11 +70,10 @@ test("if there's an error fetching the session, it should log it", async () => {
 
   await waitFor(() => {
     expect(logger.error).toHaveBeenCalledTimes(1)
-    expect(logger.error).toBeCalledWith(
-      "CLIENT_FETCH_ERROR",
-      "session",
-      new SyntaxError("Unexpected token S in JSON at position 0")
-    )
+    expect(logger.error).toBeCalledWith("CLIENT_FETCH_ERROR", {
+      path: "session",
+      error: new SyntaxError("Unexpected token S in JSON at position 0"),
+    })
   })
 })
 
diff --git a/src/client/__tests__/sign-in.test.js b/src/client/__tests__/sign-in.test.js
index a80bbeb8bb..5be0cb5025 100644
--- a/src/client/__tests__/sign-in.test.js
+++ b/src/client/__tests__/sign-in.test.js
@@ -250,11 +250,10 @@ test("when it fails to fetch the providers, it redirected back to signin page",
     expect(window.location.replace).toHaveBeenCalledWith(`/api/auth/error`)
 
     expect(logger.error).toHaveBeenCalledTimes(1)
-    expect(logger.error).toBeCalledWith(
-      "CLIENT_FETCH_ERROR",
-      "providers",
-      errorMsg
-    )
+    expect(logger.error).toBeCalledWith("CLIENT_FETCH_ERROR", {
+      error: "Error when retrieving providers",
+      path: "providers",
+    })
   })
 })
 
diff --git a/src/client/react.js b/src/client/react.js
index ee83a3aabb..2fe6bec422 100644
--- a/src/client/react.js
+++ b/src/client/react.js
@@ -320,25 +320,23 @@ export function SessionProvider(props) {
  */
 async function _fetchData(path, { ctx, req = ctx?.req } = {}) {
   try {
-    const baseUrl = await _apiBaseUrl()
     const options = req ? { headers: { cookie: req.headers.cookie } } : {}
-    const res = await fetch(`${baseUrl}/${path}`, options)
+    const res = await fetch(`${_apiBaseUrl()}/${path}`, options)
     const data = await res.json()
     if (!res.ok) throw data
     return Object.keys(data).length > 0 ? data : null // Return null if data empty
   } catch (error) {
-    logger.error("CLIENT_FETCH_ERROR", path, error)
+    logger.error("CLIENT_FETCH_ERROR", {
+      error,
+      path,
+      ...(req ? { header: req.headers } : {}),
+    })
     return null
   }
 }
 
 function _apiBaseUrl() {
   if (typeof window === "undefined") {
-    // NEXTAUTH_URL should always be set explicitly to support server side calls - log warning if not set
-    if (!process.env.NEXTAUTH_URL) {
-      logger.warn("NEXTAUTH_URL", "NEXTAUTH_URL environment variable not set")
-    }
-
     // Return absolute path when called server side
     return `${__NEXTAUTH.baseUrlServer}${__NEXTAUTH.basePathServer}`
   }
diff --git a/src/lib/errors.js b/src/lib/errors.js
index 8532b556c0..3bac54613a 100644
--- a/src/lib/errors.js
+++ b/src/lib/errors.js
@@ -32,67 +32,3 @@ export class OAuthCallbackError extends UnknownError {
 export class AccountNotLinkedError extends UnknownError {
   name = "AccountNotLinkedError"
 }
-
-export class CreateUserError extends UnknownError {
-  name = "CreateUserError"
-}
-
-export class GetUserError extends UnknownError {
-  name = "GetUserError"
-}
-
-export class GetUserByEmailError extends UnknownError {
-  name = "GetUserByEmailError"
-}
-
-export class GetUserByIdError extends UnknownError {
-  name = "GetUserByIdError"
-}
-
-export class GetUserByProviderAccountIdError extends UnknownError {
-  name = "GetUserByProviderAccountIdError"
-}
-
-export class UpdateUserError extends UnknownError {
-  name = "UpdateUserError"
-}
-
-export class DeleteUserError extends UnknownError {
-  name = "DeleteUserError"
-}
-
-export class LinkAccountError extends UnknownError {
-  name = "LinkAccountError"
-}
-
-export class UnlinkAccountError extends UnknownError {
-  name = "UnlinkAccountError"
-}
-
-export class CreateSessionError extends UnknownError {
-  name = "CreateSessionError"
-}
-
-export class GetSessionError extends UnknownError {
-  name = "GetSessionError"
-}
-
-export class UpdateSessionError extends UnknownError {
-  name = "UpdateSessionError"
-}
-
-export class DeleteSessionError extends UnknownError {
-  name = "DeleteSessionError"
-}
-
-export class CreateVerificationRequestError extends UnknownError {
-  name = "CreateVerificationRequestError"
-}
-
-export class GetVerificationRequestError extends UnknownError {
-  name = "GetVerificationRequestError"
-}
-
-export class DeleteVerificationRequestError extends UnknownError {
-  name = "DeleteVerificationRequestError"
-}
diff --git a/src/lib/logger.js b/src/lib/logger.js
index 7e2f448337..630cb27ba5 100644
--- a/src/lib/logger.js
+++ b/src/lib/logger.js
@@ -1,22 +1,37 @@
+import { UnknownError } from "./errors"
+
+/** Makes sure that error is always serializable */
+function formatError(o) {
+  if (o instanceof Error && !(o instanceof UnknownError)) {
+    return { message: o.message, stack: o.stack, name: o.name }
+  }
+  if (o?.error) {
+    o.error = formatError(o.error)
+    o.message = o.message ?? o.error.message
+  }
+  return o
+}
+
 /** @type {import("types").LoggerInstance} */
 const _logger = {
-  error(code, ...message) {
+  error(code, metadata) {
+    metadata = formatError(metadata)
     console.error(
       `[next-auth][error][${code.toLowerCase()}]`,
       `\nhttps://next-auth.js.org/errors#${code.toLowerCase()}`,
-      ...message
+      metadata.message,
+      metadata
     )
   },
-  warn(code, ...message) {
+  warn(code) {
     console.warn(
       `[next-auth][warn][${code.toLowerCase()}]`,
-      `\nhttps://next-auth.js.org/warnings#${code.toLowerCase()}`,
-      ...message
+      `\nhttps://next-auth.js.org/warnings#${code.toLowerCase()}`
     )
   },
-  debug(code, ...message) {
+  debug(code, metadata) {
     if (!process?.env?._NEXTAUTH_DEBUG) return
-    console.log(`[next-auth][debug][${code.toLowerCase()}]`, ...message)
+    console.log(`[next-auth][debug][${code.toLowerCase()}]`, metadata)
   },
 }
 
@@ -47,31 +62,19 @@ export function proxyLogger(logger = _logger, basePath) {
 
     const clientLogger = {}
     for (const level in logger) {
-      clientLogger[level] = (code, ...message) => {
-        _logger[level](code, ...message) // Log on client as usual
+      clientLogger[level] = (code, metadata) => {
+        _logger[level](code, metadata) // Logs to console
 
+        if (level === "error") {
+          metadata = formatError(metadata)
+        }
+        metadata.client = true
         const url = `${basePath}/_log`
-        const body = new URLSearchParams({
-          level,
-          code,
-          message: JSON.stringify(
-            message.map((m) => {
-              if (m instanceof Error) {
-                // Serializing errors: https://iaincollins.medium.com/error-handling-in-javascript-a6172ccdf9af
-                return { name: m.name, message: m.message, stack: m.stack }
-              }
-              return m
-            })
-          ),
-        })
+        const body = new URLSearchParams({ level, code, ...metadata })
         if (navigator.sendBeacon) {
           return navigator.sendBeacon(url, body)
         }
-        return fetch(url, {
-          method: "POST",
-          headers: { "Content-Type": "application/json" },
-          body,
-        })
+        return fetch(url, { method: "POST", body, keepalive: true })
       }
     }
     return clientLogger
diff --git a/src/server/index.js b/src/server/index.js
index efb1cdc83a..e4d00771b4 100644
--- a/src/server/index.js
+++ b/src/server/index.js
@@ -17,7 +17,7 @@ import * as state from "./lib/oauth/state-handler"
 // To work properly in production with OAuth providers the NEXTAUTH_URL
 // environment variable must be set.
 if (!process.env.NEXTAUTH_URL) {
-  logger.warn("NEXTAUTH_URL", "NEXTAUTH_URL environment variable not set")
+  logger.warn("NEXTAUTH_URL")
 }
 
 /**
@@ -43,11 +43,11 @@ async function NextAuthHandler(req, res, userOptions) {
     extendRes(req, res, resolve)
 
     if (!req.query.nextauth) {
-      const error =
+      const message =
         "Cannot find [...nextauth].js in pages/api/auth. Make sure the filename is written correctly."
 
-      logger.error("MISSING_NEXTAUTH_API_ROUTE_ERROR", error)
-      return res.status(500).end(`Error: ${error}`)
+      logger.error("MISSING_NEXTAUTH_API_ROUTE_ERROR", new Error(message))
+      return res.status(500).end(`Error: ${message}`)
     }
 
     const {
@@ -244,13 +244,8 @@ async function NextAuthHandler(req, res, userOptions) {
         case "_log":
           if (userOptions.logger) {
             try {
-              const {
-                code = "CLIENT_ERROR",
-                level = "error",
-                message = "[]",
-              } = req.body
-
-              logger[level](code, ...JSON.parse(message))
+              const { code, level, ...metadata } = req.body
+              logger[level](code, metadata)
             } catch (error) {
               // If logging itself failed...
               logger.error("LOGGER_ERROR", error)
diff --git a/src/server/lib/oauth/callback.js b/src/server/lib/oauth/callback.js
index 910ac91203..6b9e7e6356 100644
--- a/src/server/lib/oauth/callback.js
+++ b/src/server/lib/oauth/callback.js
@@ -23,13 +23,12 @@ export default async function oAuthCallback(req) {
         code = body.code
         user = body.user != null ? JSON.parse(body.user) : null
       } catch (error) {
-        logger.error(
-          "OAUTH_CALLBACK_HANDLER_ERROR",
+        logger.error("OAUTH_CALLBACK_HANDLER_ERROR", {
           error,
-          req.body,
-          provider.id,
-          code
-        )
+          body: req.body,
+          providerId: provider.id,
+          code,
+        })
         throw error
       }
     }
@@ -62,7 +61,11 @@ export default async function oAuthCallback(req) {
 
       return getProfile({ profileData, provider, tokens, user })
     } catch (error) {
-      logger.error("OAUTH_GET_ACCESS_TOKEN_ERROR", error, provider.id, code)
+      logger.error("OAUTH_GET_ACCESS_TOKEN_ERROR", {
+        error,
+        providerId: provider.id,
+        code,
+      })
       throw error
     }
   }
@@ -74,7 +77,11 @@ export default async function oAuthCallback(req) {
 
     // eslint-disable-next-line camelcase
     const { token_secret } = await client.getOAuthRequestToken(provider.params)
-    const tokens = await client.getOAuthAccessToken(oauth_token, token_secret, oauth_verifier)
+    const tokens = await client.getOAuthAccessToken(
+      oauth_token,
+      token_secret,
+      oauth_verifier
+    )
     const profileData = await client.get(
       provider.profileUrl,
       tokens.oauth_token,
@@ -113,7 +120,7 @@ export default async function oAuthCallback(req) {
 async function getProfile({ profileData, tokens, provider, user }) {
   try {
     // Convert profileData into an object if it's a string
-    if (typeof profileData === "string" || profileData instanceof String) {
+    if (typeof profileData === "string") {
       profileData = JSON.parse(profileData)
     }
 
@@ -122,7 +129,7 @@ async function getProfile({ profileData, tokens, provider, user }) {
       profileData.user = user
     }
 
-    logger.debug("PROFILE_DATA", profileData)
+    logger.debug("PROFILE_DATA", { profile: profileData })
 
     const profile = await provider.profile(profileData, tokens)
     // Return profile, raw profile and auth provider details
@@ -139,7 +146,7 @@ async function getProfile({ profileData, tokens, provider, user }) {
       },
       OAuthProfile: profileData,
     }
-  } catch (exception) {
+  } catch (error) {
     // If we didn't get a response either there was a problem with the provider
     // response *or* the user cancelled the action with the provider.
     //
@@ -147,7 +154,7 @@ async function getProfile({ profileData, tokens, provider, user }) {
     // all providers, so we return an empty object; the user should then be
     // redirected back to the sign up page. We log the error to help developers
     // who might be trying to debug this when configuring a new provider.
-    logger.error("OAUTH_PARSE_PROFILE_ERROR", exception, profileData)
+    logger.error("OAUTH_PARSE_PROFILE_ERROR", { error, profileData })
     return {
       profile: null,
       account: null,
diff --git a/src/server/lib/oauth/client.js b/src/server/lib/oauth/client.js
index 076bf33258..6aeaa0288c 100644
--- a/src/server/lib/oauth/client.js
+++ b/src/server/lib/oauth/client.js
@@ -188,7 +188,11 @@ async function getOAuth2AccessToken(code, provider, codeVerifier) {
       null,
       (error, data, response) => {
         if (error) {
-          logger.error("OAUTH_GET_ACCESS_TOKEN_ERROR", error, data, response)
+          logger.error("OAUTH_GET_ACCESS_TOKEN_ERROR", {
+            error,
+            data,
+            response,
+          })
           return reject(error)
         }
 
diff --git a/src/server/lib/oauth/pkce-handler.js b/src/server/lib/oauth/pkce-handler.js
index f15a2b0264..87ddab6f90 100644
--- a/src/server/lib/oauth/pkce-handler.js
+++ b/src/server/lib/oauth/pkce-handler.js
@@ -31,15 +31,15 @@ export async function handleCallback(req, res) {
       encryption: true,
     })
     req.options.pkce = pkce
-    logger.debug("OAUTH_CALLBACK_CHECK", "Read PKCE verifier from cookie", {
+    logger.debug("PKCE_VERIFIER_FROM_COOKIE", {
       code_verifier: pkce.code_verifier,
       pkceLength: PKCE_LENGTH,
       method: PKCE_CODE_CHALLENGE_METHOD,
     })
     // remove PKCE after it has been used
-    cookie.set(res, cookies.pkceCodeVerifier.name, "", { 
+    cookie.set(res, cookies.pkceCodeVerifier.name, "", {
       ...cookies.pkceCodeVerifier.options,
-      maxAge: 0 
+      maxAge: 0,
     })
   } catch (error) {
     logger.error("CALLBACK_OAUTH_ERROR", error)
@@ -61,7 +61,7 @@ export async function handleSignin(req, res) {
     }
     // Started login flow, add generated pkce to req.options and (encrypted) code_verifier to a cookie
     const pkce = pkceChallenge(PKCE_LENGTH)
-    logger.debug("OAUTH_SIGNIN_CHECK", "Created PKCE challenge/verifier", {
+    logger.debug("CREATE_PKCE_CHALLENGE_VERIFIER", {
       ...pkce,
       pkceLength: PKCE_LENGTH,
       method: PKCE_CODE_CHALLENGE_METHOD,
@@ -86,10 +86,7 @@ export async function handleSignin(req, res) {
       expires: cookieExpires.toISOString(),
       ...cookies.pkceCodeVerifier.options,
     })
-    logger.debug(
-      "OAUTH_SIGNIN_CHECK",
-      "Created PKCE code_verifier saved in cookie"
-    )
+    logger.debug("PKCE_CODE_VERIFIER_SAVED", { encryptedCodeVerifier })
   } catch (error) {
     logger.error("SIGNIN_OAUTH_ERROR", error)
     return res.redirect(`${baseUrl}${basePath}/error?error=OAuthSignin`)
diff --git a/src/server/lib/oauth/state-handler.js b/src/server/lib/oauth/state-handler.js
index 722af0d309..a1cacf4c41 100644
--- a/src/server/lib/oauth/state-handler.js
+++ b/src/server/lib/oauth/state-handler.js
@@ -20,11 +20,7 @@ export async function handleCallback(req, res) {
     const state = req.query.state || req.body.state
     const expectedState = createHash("sha256").update(csrfToken).digest("hex")
 
-    logger.debug(
-      "OAUTH_CALLBACK_CHECK",
-      "Comparing received and expected state",
-      { state, expectedState }
-    )
+    logger.debug("STATE_CHECK", { state, expectedState })
     if (state !== expectedState) {
       throw new OAuthCallbackError("Invalid state returned from OAuth provider")
     }
@@ -51,11 +47,7 @@ export async function handleSignin(req, res) {
     const state = createHash("sha256").update(csrfToken).digest("hex")
 
     provider.authorizationParams = { ...provider.authorizationParams, state }
-    logger.debug(
-      "OAUTH_CALLBACK_CHECK",
-      "Added state to authorization params",
-      { state }
-    )
+    logger.debug("STATE_ADDED_TO_PARAMS", { state })
   } catch (error) {
     logger.error("SIGNIN_OAUTH_ERROR", error)
     return res.redirect(`${baseUrl}${basePath}/error?error=OAuthSignin`)
diff --git a/src/server/lib/signin/oauth.js b/src/server/lib/signin/oauth.js
index 55f2138a78..3f08e3b578 100644
--- a/src/server/lib/signin/oauth.js
+++ b/src/server/lib/signin/oauth.js
@@ -33,7 +33,7 @@ export default async function getAuthorizationUrl(req) {
       url = url.replace(baseUrl, provider.authorizationUrl + "&")
     }
 
-    logger.debug("GET_AUTHORIZATION_URL", url)
+    logger.debug("GET_AUTHORIZATION_URL", { url, params })
     return url
   }
 
@@ -44,7 +44,7 @@ export default async function getAuthorizationUrl(req) {
       oauth_token_secret: tokens.oauth_token_secret,
       ...tokens.params,
     })}`
-    logger.debug("GET_AUTHORIZATION_URL", url)
+    logger.debug("GET_AUTHORIZATION_URL", { url, tokens })
     return url
   } catch (error) {
     logger.error("GET_AUTHORIZATION_URL_ERROR", error)
diff --git a/src/server/routes/callback.js b/src/server/routes/callback.js
index 7f620f5ee7..510581fcc3 100644
--- a/src/server/routes/callback.js
+++ b/src/server/routes/callback.js
@@ -303,7 +303,9 @@ export default async function callback(req, res) {
     if (!useJwtSession) {
       logger.error(
         "CALLBACK_CREDENTIALS_JWT_ERROR",
-        "Signin in with credentials is only supported if JSON Web Tokens are enabled"
+        new Error(
+          "Signin in with credentials is only supported if JSON Web Tokens are enabled"
+        )
       )
       return res
         .status(500)
@@ -313,7 +315,9 @@ export default async function callback(req, res) {
     if (!provider.authorize) {
       logger.error(
         "CALLBACK_CREDENTIALS_HANDLER_ERROR",
-        "Must define an authorize() handler to use credentials authentication provider"
+        new Error(
+          "Must define an authorize() handler to use credentials authentication provider"
+        )
       )
       return res
         .status(500)
diff --git a/types/index.d.ts b/types/index.d.ts
index 8b2d4fd086..e5d0a737f6 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -213,9 +213,22 @@ export type Theme = "auto" | "dark" | "light"
  * [Documentation](https://next-auth.js.org/configuration/options#logger)
  */
 export interface LoggerInstance {
-  warn(code: string, ...message: unknown[]): void
-  error(code: string, ...message: unknown[]): void
-  debug(code: string, ...message: unknown[]): void
+  warn(
+    code:
+      | "JWT_AUTO_GENERATED_SIGNING_KEY"
+      | "JWT_AUTO_GENERATED_ENCRYPTION_KEY"
+      | "NEXTAUTH_URL"
+  ): void
+  error(
+    code: string,
+    /**
+     * Either an instance of (JSON serializable) Error
+     * or an object that contains some debug information.
+     * (Error is still available through `metadata.error`)
+     */
+    metadata: Error | { error: Error; [key: string]: unknown }
+  ): void
+  debug(code: string, metadata: unknown): void
 }
 
 /**
diff --git a/www/docs/configuration/options.md b/www/docs/configuration/options.md
index 401e782cfe..f1ebe05198 100644
--- a/www/docs/configuration/options.md
+++ b/www/docs/configuration/options.md
@@ -329,6 +329,8 @@ Set debug to `true` to enable debug messages for authentication and database ope
 
 Override any of the logger levels (`undefined` levels will use the built-in logger), and intercept logs in NextAuth. You can use this to send NextAuth logs to a third-party logging service.
 
+The `code` parameter for `error` and `warn` are explained in the [Warnings](/warnings) and [Errors](/errors) pages respectively.
+
 Example:
 
 ```js title="/pages/api/auth/[...nextauth].js"
@@ -337,14 +339,14 @@ import log from "logging-service"
 export default NextAuth({
   ...
   logger: {
-    error(code, ...message) {
-      log.error(code, message)
+    error(code, metadata) {
+      log.error(code, metadata)
     },
-    warn(code, ...message) {
-      log.warn(code, message)
+    warn(code) {
+      log.warn(code)
     },
-    debug(code, ...message) {
-      log.debug(code, message)
+    debug(code, metadata) {
+      log.debug(code, metadata)
     }
   }
   ...