article Resolve Synthetic Browser Monitor Error Codes in Dynatrace in Troubleshooting

Resolve Synthetic Browser Monitor Error Codes in Dynatrace

xu_guo — Tue, 09 Dec 2025 07:45:23 GMT

Summary

This article provides the most common error codes seen in Dynatrace Synthetic browser monitors, along with note on the behavior and some troubleshooting suggestions.

For any HTTP Response code errors, follow the troubleshooting steps here.

For connection issues, check Firewall Constraints and allowlisting for Synthetic Monitoring

Error Codes

Error	Detail	Test fails	Error category	Notes
400	Bad Request	Yes	HTTP response code	All errors are reported in the same tab
401	Unauthorized	Yes	HTTP response code	gets reported in a same tab since APM-108556
402	Payment Required	Yes	HTTP response code
403	Forbidden	Yes	HTTP response code
404	Not Found	Yes	HTTP response code
405	Method Not Allowed	Yes	HTTP response code
406	Not Acceptable	Yes	HTTP response code
407	Proxy Authentication Required	Yes	HTTP response code
408	Request Timeout	Yes	HTTP response code
409	Conflict	Yes	HTTP response code
410	Gone	Yes	HTTP response code
411	Length Required	Yes	HTTP response code
412	Precondition Required	Yes	HTTP response code
413	Request Entry Too Large	Yes	HTTP response code
414	Request-URI Too Long	Yes	HTTP response code
415	Unsupported Media Type	Yes	HTTP response code
416	Requested Range Not Satisfiable	Yes	HTTP response code
417	Expectation Failed	Yes	HTTP response code
418	I am a Teapot	Yes	HTTP response code
419	Authentication Timeout	Yes	HTTP response code
420	Method failure	Yes	HTTP response code
421	Misdirected Request	Yes	HTTP response code
422	Unprocessable Entity	Yes	HTTP response code
423	Locked	Yes	HTTP response code
424	Failed Dependency	Yes	HTTP response code
425	Unordered Collection	Yes	HTTP response code
426	Upgrade Required	Yes	HTTP response code
428	Precondition Required	Yes	HTTP response code
429	Too many requests	Yes	HTTP response code
431	Request Header fields too large	Yes	HTTP response code
440	Login Timeout	Yes	HTTP response code
444	No Response	Yes	HTTP response code
449	Retry with	Yes	HTTP response code
450	Blocked by Windows Parental Controls	Yes	HTTP response code
451	Unavailable for Legal Reasons	Yes	HTTP response code
456	Unspecified Error	Yes	HTTP response code
457	Unspecified Error	Yes	HTTP response code
494	Request Header too large	Yes	HTTP response code
495	Cert Error	Yes	HTTP response code
496	No Cert	Yes	HTTP response code
497	Http to Https	Yes	HTTP response code
498	Token Expired Invalid	Yes	HTTP response code
499	Client Closed Request	Yes	HTTP response code
500	Internal Server Error	Yes	HTTP response code
501	Not Implemented	Yes	HTTP response code
502	Bad Gateway	Yes	HTTP response code
503	Service Unavailable	Yes	HTTP response code
504	Gateway Timeout	Yes	HTTP response code
505	HTTP Version Not Supported	Yes	HTTP response code
506	Variant also Negotiates	Yes	HTTP response code
507	Insufficient Storage	Yes	HTTP response code
508	Loop detected	Yes	HTTP response code
509	Bandwidth limit exceeded	Yes	HTTP response code
510	Not extended	Yes	HTTP response code
511	Network authentication required	Yes	HTTP response code
520	Webserver is returning an unknown error	Yes	HTTP response code
521	Web Server is down	Yes	HTTP response code
522	Connection timed out	Yes	HTTP response code
524	A timeout occurred	Yes	HTTP response code
598	Network read timeout error	Yes	HTTP response code
599	Network connect timeout error	Yes	HTTP response code
1001	unsupported script version	Yes	Script error	from recorder and in responsecode.js → moved to errorlist Triggered when the script has no version or the version is neither 1.0 nor 2.0
1002	script syntax error	Yes	Script error	from recorder and in responsecode.js → moved to errorlist It's triggered when parsing the gslScript fails
1010	File downloads are currently not supported	Yes	Script error	The script has clicked on something that is trying to download a file. This is not allowed in Browser Monitors
1301	Hard / Transaction Timeout	Yes	Transaction Timeout	Transaction deadline of 5 min exceeded. Can be set via test configuration but not via the UI (transactionTimeout)
1302	Step Timeout	Yes	Step Timeout	Step deadline of 60s exceeded. Can be set via test configuration but not via the UI (stepTimeout)
1304	Wait for Page Complete Timeout / Time exceeded waiting for page to load completely	Yes	Step Timeout	Error code is thrown if the step deadline is exceeded while waiting for this
1305	Wait Network Timeout / Time exceeded waiting for background network activity to complete	Yes	Step Timeout	Error code is thrown if the step deadline is exceeded while waiting for this
1306	Wait for validate Timeout	Yes	User Script Failure	Error code is thrown if the step deadline is exceeded while waiting for this
1307	Wait timeout was too short for the page to load	Yes	Step Timeout	Error code is thrown when user defined wait timeout was too short for the page to load. This should be fixed within the test. (Increasing the wait timeout or change it to another wait condition; ea. "Wait for page to load completely")
1401	Validate Text Match Failed / One or more validations created for this action have failed	Yes	Content match failed	not generic error message any more, not used as it is but rather a detailed message of which element validation is failed
1501	Clickpath action failure	Yes	User Script Failure	This is also the default error in case we can't find the corresponding error type for an error. Usually, it means there's a bug somewhere in our code.
1502	Locator failure "The html element could not be found to perform action"	Yes	User Script Failure	A special case of 1501 Clickpath action failure where the failure was caused by missing or wrong locators so mainly locator failure. The player couldn't find the element to click on but if the validation before is not set to fail then it won't be a validation timeout error. 1501 will stay the default error in case we don't want to show the details of the error to the user (as it might be an internal error/exception)
1601	JS execution took too long	Yes	JS step errors	JS execution has a shorter limit than a normal step
1602	Exception was thrown	Yes	JS step errors	An exception occurred while the custom script was executing
1603	Test marked as failed by the user	Yes	JS step errors	The user itself marked the test as failed
1701	The specified target window is not found	Yes	Player error	The target window specified in the script was not found, either it was specified by mistake by the customer or the recorder record it wrongly.
1702	The specified target window got disconnected	Yes	Player error	The target window to event is using has been disconnected, usually this is where the window closes before the event has completed.
1801	Undefined placeholder was used	Yes	Script placeholders	Placeholder was used but was not defined
2001	playback window was closed	Yes	Recorder error	from recorder
2002	playback window was minimized	Yes	Recorder error	from recorder
2003	Extension is not enabled in incognito	Yes	Recorder error	from recorder (not defined in cluster), the text may change, behind a feature flag
2004	There is another incognito window open that needs to be closed first	Yes	Recorder error	from recorder (not defined in cluster), the text may change, behind a feature flag
10054	Connection Reset	Yes	Chrome net error	ERR_CONNECTION_RESET is caused by issues that prevent a stable connection between your browser and a website. The problem usually originates from misconfigurations in the visitor's device or network. However, temporary connectivity issues or firewall restrictions from a website's web server can also cause the error. https://stackoverflow.com/questions/1434451/what-does-connection-reset-by-peer-mean
12000	Default network error	Yes	Chrome net error	This error is thrown when we get an unknown / new chrome network error which does not fit any other error. Since sprint 168 It will be here https://github.com/adobe/chromium/blob/master/net/base/net_error_list.h but not in our list.
12006	The site reported UNEXPECTED		Chrome net error	Chrome network error:net::ERR_UNEXPECTED error. This is usually caused by an authentication issue. Try curling to the application from the ActiveGate, do you get a successful response? Often it is the case that a proxy is required to allow the ActiveGate to access the application. Or if you are already using a proxy, possibly you need to bypass it for the affected application. You can see the different scenarios available here. Potential mitigation of this error is ignoring it using this experimental flag in Browser Monitor script: { "configuration": { "experimentalProperties": [{ "name": "IgnoreHttp2UnexpectedError", "value": "true" }] } }
12010	Failed		Chrome net error	Chrome network error net::ERR_FAILED It sometimes shows up for CORS errors. If you playback the monitor locally, you can often get more information on the error from DevTools console.
12012	Address Unreachable	Yes	Chrome net error
12013	DNS Lookup Failure	Yes	Chrome net error
12014	Connection Timeout	Yes	Connection error Chrome net error	This error can be caused from 2 places, as an exception to cancel transaction when connectionTimeoutExceeded or as a chrome network error net::ERR_CONNECTION_TIMED_OUT. The first is when it takes so long to receive a response from the server. By default it's a 59 seconds unless specified otherwise in the script.
12015	Unsafe Port	Yes	Chrome net error
12016	Connection Refused	Yes	Chrome net error
12017	Too many redirects	Yes	Chrome net error	not in recorder This error is handled as netWorkError and it sets a connection error similar to 12014
12018	There is no Internet connection	Yes	Chrome net error	new in case of emulateNetworkConditions true and offline true
12019	Request was blocked by client / Malicious resource detected	Yes	Chrome net error but triggered by us	In case of coin mining url, we block the web request and report the error as it's reported by chrome.
12020	The site unexpectedly closed the connection	Yes	Chrome net error	Since sprint 142, in case a connection is closed from the server / proxy / firewall side.
12026	The site reported ERR_SPDY_INADEQUATE_TRANSPORT_SECURITY	Yes	Chrome net error	Since sprint 162
12027	The site reported ERR_EMPTY_RESPONSE	Yes	Chrome net error	Since sprint 167
12032	The site reported ERR_SSL_VERSION_INTERFERENCE	Yes	Chrome net error	Since sprint 168
12033	The site reported ERR_TIMED_OUT	Yes	Chrome net error	Since sprint 168
12034	The site reported ERR_BLOCKED_BY_CLIENT	Yes	Chrome net error	Something is preventing a webpage from loading certain resources. Check antivirus and firewall settings. Check troubleshooting steps in Firewall Constraints and allowlisting for Synthetic Monitoring
12035	The site reported ERR_SSL_PROTOCOL_ERROR	Yes	Chrome net error	For private locations, try disabling QUIC protocol, see Error code 12161. Check the AV settings. Check TLS versions used.
12047	The site reported ERR_TUNNEL_CONNECTION_FAILED	Yes	Chrome net error	For private locations, confirm proxy details are correct in custom.properties. See proxy scenario documentation
12049	The site reported ERR_SSL_CLIENT_AUTH_CERT_NEEDED	Yes	Chrome net error	How to avoid the Synthetic Browser monitor Error Code 12049 "ERR_SSL_CLIENT_AUTH_CERT_NEEDED"
12143	The site reported HTTP2_PROTOCOL_ERROR	Yes	Chrome net error	May be caused by firewalls like Akamai. In these cases, add Synthetic Browser Monitor traffic to the firewall allow list.
12161	The site reported QUIC_PROTOCOL_ERROR	Yes	Chrome net error	For private locations, you can disable QUIC protocol, by adding the following line to the user.properties file com.ruxit.vuc.poolConfig.playerConfig.additionalStartupParams=--disable-quic Linux: Update /var/lib/dynatrace/synthetic/config/user.properties and then restart the vuc.service. Windows: C:\ProgramData\dynatrace\synthetic\config\user.properties and then restart the Dynatrace Synthetic Gateway service.
12183	The site reported HTTP_RESPONSE_CODE_FAILURE	Yes	Chrome net error	This is a generic error which you need to check further into. It's alerting you to a status code that is not considered successful, usually 401, 404, 500 etc. Checking the screenshot is usually sufficient but if that does not reveal anything, you can check the waterfall and execution log (see Synthetic Player (VUP) logs section here)
20000	Unspecified Event Type Error	Yes	User Script Failure	Internal error when the event we want to simulate is unspecified. Should not happen.
20001	INVALID_USER_AGENT	Yes	User Script Failure	User Agent is Missing RuxitSynthetic part with test id and run id
20002	ABORT_PSR_ERROR	Yes	User Script Failure	Chrome startup error

What's Next

If this article didn't help resolve the issue, open a chat and provide

a link to the browser monitor that you are troubleshooting.
an explanation of the behavior you are seeing, and what you are expecting.
the troubleshooting steps you have already completed.

You can find further troubleshooting tips for Synthetic in the Synthetic Troubleshooting Map

Re: Synthetic Browser Monitor Error Codes

AntonioSousa — Sun, 27 Nov 2022 11:04:20 GMT

@xu_guo,

Thanks a lot! I believe these codes should also be in the documentation.

BTW, do the 97? codes also appear in synthetics?
https://www.dynatrace.com/support/help/how-to-use-dynatrace/real-user-monitoring/setup-and-configuration/web-applications/additional-configuration/configure-errors

Re: Synthetic Browser Monitor Error Codes

pathak_vivek — Wed, 30 Nov 2022 10:40:03 GMT

Hi @xu_guo

Do you have any idea how to get past and fix the error 12020 - The site unexpectedly closed the connection.

Re: Synthetic Browser Monitor Error Codes

Ahmed_Khaled — Tue, 16 May 2023 05:58:26 GMT

There is also an error code 12006 Site Reported Unexpected, if anyone has experience with that.

Re: Synthetic Browser Monitor Error Codes

HannahM — Tue, 16 May 2023 16:47:23 GMT

12006 Site Reported Unexpected is the Chrome ERR_UNEXPECTED error. This is usually caused by an authentication issue. If you curl to the application from the ActiveGate, do you get a successful response? Often it is the case that a proxy is required to allow the ActiveGate to access the application. Or if you are already using a proxy, possibly you need to bypass it for the affected application. You can see the different scenarios available here

Re: Synthetic Browser Monitor Error Codes

Sravanth — Thu, 31 Aug 2023 07:37:21 GMT

Hello,

We're observing "The request failed with error 12100: ABORTED", any idea what exactly this means? and possible causes?

Couldn't find any details in the docs.

Thanks,

Sravanth.

Re: Synthetic Browser Monitor Error Codes

HannahM — Wed, 06 Sep 2023 10:37:20 GMT

"The request failed with error 12100: ABORTED" is seen where the request got aborted, and the browser doesn't provide any more details. Do you see the same in DevTools?

Re: Synthetic Browser Monitor Error Codes

Sravanth — Thu, 14 Sep 2023 07:19:45 GMT

Hi @HannahM ,

No, we observe this error only in waterfall analysis of the synthetic executions and is intermittent with no real trend.

Re: Synthetic Browser Monitor Error Codes

HannahM — Thu, 14 Sep 2023 09:14:54 GMT

OK, I would open a chat in the WebUI and provide a link to monitor and if possible a Har from when the page was loaded. Thanks

Re: Synthetic Browser Monitor Error Codes

jordan_rose — Fri, 22 Sep 2023 11:15:35 GMT

Are these codes in the doc anywhere?

What does this one mean?

"healthStatusCode": 17,
"healthStatus": "CONSTRAINT_VIOLATED_VALUE",

Re: Synthetic Browser Monitor Error Codes

HannahM — Fri, 22 Sep 2023 11:41:23 GMT

Is that from a Browser Monitor or HTTP Monitor? We mention it here for HTTP Monitors

Re: Synthetic Browser Monitor Error Codes

Vaishnavi_Ubhe — Wed, 04 Oct 2023 04:30:55 GMT

@HannahM

Can you please tell me how to resolve the 403 error of the synthetic monitor?

The URL is getting loaded when I try in the browser, but somehow, it is throwing a 403 error in Dynatrace.

I have created RUM for this application, but no user actions are getting captured, to troubleshoot this I created the synthetic monitor which is throwing a 403 error.

Can you please help me with this?

Re: Synthetic Browser Monitor Error Codes

AntonPineiro — Wed, 04 Oct 2023 06:57:32 GMT

Hi @Vaishnavi_Ubhe,

Is your synthetic running against public Dynatrace robot? Private location?

Best regards

Re: Synthetic Browser Monitor Error Codes

Vaishnavi_Ubhe — Wed, 04 Oct 2023 07:18:46 GMT

@AntonPineiro

Is it running against a private location.

Re: Synthetic Browser Monitor Error Codes

HannahM — Wed, 04 Oct 2023 08:08:23 GMT

403 is a forbidden error. Have you added credentials to the monitor to allow it access? If you open the page from the Private location does it have access? Sometimes customers need to explicitly allow certain machines to have access using a proxy or network rules.

Re: Synthetic Browser Monitor Error Codes

alexandre_clava — Wed, 20 Dec 2023 10:02:45 GMT

Hi,

I have the same behavior (intermittent as well).

Did you found the root cause and/or a fix ?

Best regards

Alexandre

Hello,

We're observing "The request failed with error 12100: ABORTED", any idea what exactly this means? and possible causes?

Couldn't find any details in the docs.

Thanks,

Sravanth.

Re: Synthetic Browser Monitor Error Codes

ScottD — Mon, 05 Feb 2024 13:31:05 GMT

You're missing "1702 - The specified target window got disconnected".

Re: Synthetic Browser Monitor Error Codes

AntonioSousa — Thu, 02 May 2024 20:45:41 GMT

I have observed today in a waterfall:

This request failed with error 12101: FAILED.

Haven't found any reference to it. What might it mean?

Re: Synthetic Browser Monitor Error Codes

HannahM — Fri, 03 May 2024 11:00:00 GMT

"This request failed with error 12101: FAILED." is what the Browser monitor shows for resources when Chrome returns

net::ERR_FAILED

Unfortunately, it's quite a generic error. It sometimes shows up for CORS errors. If you playback the monitor locally, you can often get more information on the error from DevTools console, assuming it's not intermittent.

Re: Synthetic Browser Monitor Error Codes

CTull — Fri, 10 May 2024 00:22:42 GMT

l will add to the Horizon vmware application I am randomly getting this error.

12183 - The site reported HTTP_RESPONSE_CODE_FAILURE