For the past couple months we were debugging an issue in one of our websites and finally where able to narrow it down to some encoding mismatch. For some requests made from mobile devices, explicitly requesting gzip/deflate compressed content, Cloudflare is responding with brotli compressed content, which leads to a net::ERR_CONTENT_DECODING_FAILED on the device itself.
Following a “mocked” request via curl:
curl 'https://domain.tld/_next/static/chunks/8956-a1e057f6fc38402b.js' -H 'authority: domain.tld' -H 'accept: _/_' -H 'accept-language: en-US,en;q=0.9' -H 'cookie: [...stripped...]' -H 'referer: https://domain.tld/' -H 'sec-fetch-dest: script' -H 'sec-fetch-mode: no-cors' -H 'sec-fetch-site: same-origin' -H 'user-agent: Mozilla/5.0 (Linux; Android 13; Pixel 4 Build/TP1A.221005.002.B2; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/118.0.0.0 Mobile Safari/537.36 Cordova' -H 'x-requested-with: tld.domain.mobileapp' --compressed -v -o /dev/null
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0\* Trying 104.26.15.143:443...
- Connected to domain.tld (104.26.15.143) port 443 (#0)
- ALPN: offers h2,http/1.1
- (304) (OUT), TLS handshake, Client hello (1):
} [322 bytes data]
- CAfile: /etc/ssl/cert.pem
- CApath: none
- (304) (IN), TLS handshake, Server hello (2):
{ [122 bytes data]
- (304) (IN), TLS handshake, Unknown (8):
{ [19 bytes data]
- (304) (IN), TLS handshake, Certificate (11):
{ [4225 bytes data]
- (304) (IN), TLS handshake, CERT verify (15):
{ [264 bytes data]
- (304) (IN), TLS handshake, Finished (20):
{ [36 bytes data]
- (304) (OUT), TLS handshake, Finished (20):
} [36 bytes data]
- SSL connection using TLSv1.3 / AEAD-CHACHA20-POLY1305-SHA256
- ALPN: server accepted h2
- Server certificate:
- subject: CN=domain.tld
- start date: Oct 23 19:31:28 2023 GMT
- expire date: Jan 21 19:31:27 2024 GMT
- subjectAltName: host "domain.tld" matched cert's "\*.domain.tld"
- issuer: C=US; O=Google Trust Services LLC; CN=GTS CA 1P5
- SSL certificate verify ok.
- using HTTP/2
- h2 [:method: GET]
- h2 [:scheme: https]
- h2 [:authority: domain.tld]
- h2 [:path: /_next/static/chunks/8956-a1e057f6fc38402b.js]
- h2 [accept-encoding: deflate, gzip]
- h2 [authority: domain.tld]
- h2 [accept: */*]
- h2 [accept-language: en-US,en;q=0.9]
- h2 [cookie: [...stripped...]]
- h2 [referer: https://domain.tld/]
- h2 [sec-fetch-dest: script]
- h2 [sec-fetch-mode: no-cors]
- h2 [sec-fetch-site: same-origin]
- h2 [user-agent: Mozilla/5.0 (Linux; Android 13; Pixel 4 Build/TP1A.221005.002.B2; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/118.0.0.0 Mobile Safari/537.36 Cordova]
- h2 [x-requested-with: tld.domain.mobileapp]
- Using Stream ID: 1 (easy handle 0x136815400)
> GET /\_next/static/chunks/8956-a1e057f6fc38402b.js HTTP/2
> Host: domain.tld
> Accept-Encoding: deflate, gzip
> authority: domain.tld
> accept: _/_
> accept-language: en-US,en;q=0.9
> cookie: [...stripped...]
> referer: https://domain.tld/
> sec-fetch-dest: script
> sec-fetch-mode: no-cors
> sec-fetch-site: same-origin
> user-agent: Mozilla/5.0 (Linux; Android 13; Pixel 4 Build/TP1A.221005.002.B2; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/118.0.0.0 Mobile Safari/537.36 Cordova
> x-requested-with: tld.domain.mobileapp
>
> < HTTP/2 200
> < date: Fri, 03 Nov 2023 12:41:48 GMT
> < content-type: application/javascript; charset=utf-8
> < access-control-allow-origin: \*
> < cache-control: public, max-age=315360000
> < content-disposition: inline; filename="8956-a1e057f6fc38402b.js"
> < content-encoding: br
> < etag: W/"9b7153177c56de770369517eb6ec3388"
> < strict-transport-security: max-age=63072000; includeSubDomains; preload
> < x-matched-path: /\_next/static/chunks/8956-a1e057f6fc38402b.js
> < x-vercel-cache: HIT
> < x-vercel-id: dub1::fcmnh-1698331720154-8cd6e65c32a5
> < expires: Thu, 31 Dec 2037 23:55:55 GMT
> < vary: Accept-Encoding, User-Agent
> < cf-cache-status: HIT
> < age: 285967
> < report-to: {"endpoints":[{"url":"https:\/\/a.nel.cloudflare.com\/report\/v3?s=4cA%2FR3YYBG26Zlego9ZKrd7Bms3XRnU5XPL5HXo%2FxeTPAmkIB5RenlyV61kZVSB8Q400ylUJOweUW7drWxRsaIQ6r1kSfkEL%2BROKlebMDf8wk%2Fk8oAcIXRVrvnmg%2BqGboRz8"}],"group":"cf-nel","max_age":604800}
> < nel: {"success_fraction":0,"report_to":"cf-nel","max_age":604800}
> < server: cloudflare
> < cf-ray: 8204b18bdde91e6a-FRA
> < alt-svc: h3=":443"; ma=86400
> <
> { [1360 bytes data]
- Unrecognized content encoding type. libcurl understands deflate, gzip content encodings.
100 1360 0 1360 0 0 16213 0 --:--:-- --:--:-- --:--:-- 17662
- Connection #0 to host domain.tld left intact
curl: (61) Unrecognized content encoding type. libcurl understands deflate, gzip content encodings.
Is this expected?