diff --git a/docs/readme.md b/docs/readme.md
index d0c5ebc8..e498dadc 100644
--- a/docs/readme.md
+++ b/docs/readme.md
@@ -76,6 +76,53 @@ const retryingDbProfile = withRetrying(dbProfile, {
 const client = createClient(retryingDbProfile, 'my-awesome-program')
 ```
 
+## Logging requests
+
+You can use `profile.logRequest` and `profile.logResponse` to process the raw [Fetch](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API) [`Request`](https://developer.mozilla.org/en-US/docs/Web/API/Request) and [`Response`](https://developer.mozilla.org/en-US/docs/Web/API/Response), respectively.
+
+As an example, we can implement a custom logger:
+
+```js
+const createClient = require('hafas-client')
+const dbProfile = require('hafas-client/p/db')
+
+const logRequest = (ctx, fetchRequest) => {
+	// ctx looks just like with the other profile.* hooks:
+	const {profile, opt} = ctx
+
+	console.debug(fetchRequest.headers, fetchRequest.body + '')
+}
+
+// create a client with Deutsche Bahn profile that debug-logs
+const client = createClient({
+	...dbProfile,
+	logRequest,
+	logResponse,
+}, 'my-awesome-program')
+```
+
+```js
+// logRequest output:
+{
+	accept: 'application/json',
+	'accept-encoding': 'gzip, br, deflate',
+	'content-type': 'application/json',
+	connection: 'keep-alive',
+	'user-agent': 'hafas842c51-clie842c51nt debug C842c51LI'
+} {"lang":"de","svcReqL":[{"cfg":{"polyEnc":"GPA"},"meth":"LocMatch",…
+// logResponse output:
+{
+	'content-encoding': 'gzip',
+	'content-length': '1010',
+	'content-type': 'application/json; charset=utf-8',
+	date: 'Thu, 06 Oct 2022 12:31:09 GMT',
+	server: 'Apache',
+	vary: 'User-Agent'
+} {"ver":"1.45","lang":"deu","id":"sb42zgck4mxtxm4s","err":"OK","graph"…
+```
+
+The default `profile.logRequest` [`console.error`](https://nodejs.org/docs/latest-v10.x/api/console.html#console_console_error_data_args)s the request body, if you have set `$DEBUG` to `hafas-client`. Likewise, `profile.logResponse` `console.error`s the response body.
+
 ## Writing a profile
 
 Check [the guide](writing-a-profile.md).
diff --git a/lib/default-profile.js b/lib/default-profile.js
index 09a6e62d..973545cd 100644
--- a/lib/default-profile.js
+++ b/lib/default-profile.js
@@ -47,6 +47,14 @@ const formatLocation = require('../format/location')
 const formatRectangle = require('../format/rectangle')
 const filters = require('../format/filters')
 
+const DEBUG = /(^|,)hafas-client(,|$)/.test(process.env.DEBUG || '')
+const logRequest = DEBUG
+	? (_, req) => console.error(req.body + '')
+	: () => {}
+const logResponse = DEBUG
+	? (_, res, body) => console.error(body)
+	: () => {}
+
 const id = (ctx, x) => x
 
 const defaultProfile = {
@@ -56,6 +64,8 @@ const defaultProfile = {
 	salt: null,
 	addChecksum: false,
 	addMicMac: false,
+	logRequest,
+	logResponse,
 
 	formatStationBoardReq,
 	formatLocationsReq,
diff --git a/lib/request.js b/lib/request.js
index bd976052..edc8203b 100644
--- a/lib/request.js
+++ b/lib/request.js
@@ -1,7 +1,6 @@
 'use strict'
 
 const DEV = process.env.NODE_ENV === 'dev'
-const DEBUG = /(^|,)hafas-client(,|$)/.test(process.env.DEBUG || '')
 
 const ProxyAgent = require('https-proxy-agent')
 const {isIP} = require('net')
@@ -13,7 +12,7 @@ const pick = require('lodash/pick')
 const captureStackTrace = DEV ? require('capture-stack-trace') : () => {}
 const {stringify} = require('qs')
 const Promise = require('pinkie-promise')
-const {fetch} = require('fetch-ponyfill')({Promise})
+const {Request, fetch} = require('fetch-ponyfill')({Promise})
 const {parse: parseContentType} = require('content-type')
 const {addErrorInfo} = require('./errors')
 
@@ -99,7 +98,6 @@ const request = (ctx, userAgent, reqData) => {
 		redirect: 'follow',
 		query: {}
 	})
-	if (DEBUG) console.error(req.body)
 
 	if (profile.addChecksum || profile.addMicMac) {
 		if (!Buffer.isBuffer(profile.salt) && 'string' !== typeof profile.salt) {
@@ -126,6 +124,8 @@ const request = (ctx, userAgent, reqData) => {
 	}
 
 	const url = profile.endpoint + '?' + stringify(req.query)
+	const fetchReq = new Request(url, req)
+	profile.logRequest(ctx, fetchReq)
 
 	// Async stack traces are not supported everywhere yet, so we create our own.
 	const err = new Error()
@@ -134,7 +134,7 @@ const request = (ctx, userAgent, reqData) => {
 	err.url = url
 	captureStackTrace(err)
 
-	return fetch(url, req)
+	return fetch(fetchReq)
 	.then((res) => {
 		err.statusCode = res.status
 		if (!res.ok) {
@@ -151,29 +151,31 @@ const request = (ctx, userAgent, reqData) => {
 				throw err
 			}
 		}
-		return res.json()
-	})
-	.then((b) => {
-		if (DEBUG) console.error(JSON.stringify(b))
 
-		if (b.err && b.err !== 'OK') {
-			addErrorInfo(err, b.err, b.errTxt, b.id)
-			throw err
-		}
-		if (!b.svcResL || !b.svcResL[0]) {
-			err.message = 'invalid response'
-			throw err
-		}
-		if (b.svcResL[0].err !== 'OK') {
-			addErrorInfo(err, b.svcResL[0].err, b.svcResL[0].errTxt, b.id)
-			throw err
-		}
+		return res.text()
+		.then((body) => {
+			profile.logResponse(ctx, res, body)
+			const b = JSON.parse(body)
 
-		const res = b.svcResL[0].res
-		return {
-			res,
-			common: profile.parseCommon({...ctx, res})
-		}
+			if (b.err && b.err !== 'OK') {
+				addErrorInfo(err, b.err, b.errTxt, b.id)
+				throw err
+			}
+			if (!b.svcResL || !b.svcResL[0]) {
+				err.message = 'invalid response'
+				throw err
+			}
+			if (b.svcResL[0].err !== 'OK') {
+				addErrorInfo(err, b.svcResL[0].err, b.svcResL[0].errTxt, b.id)
+				throw err
+			}
+
+			const svcRes = b.svcResL[0].res
+			return {
+				res: svcRes,
+				common: profile.parseCommon({...ctx, res: svcRes}),
+			}
+		})
 	})
 }