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Common HAR Findings Explained

HAR files are useful for getting information on website performance problems. Here’s a list of common findings.

DNS cannot be resolved

Technical problem
The URL cannot be resolved to an IP address.

The user’s perspective
The user enters the URL but gets a browser error message indicating that the browser does not know where to connect to.

Comments
The comment is pretty clear, here: “DNS lookup for … failed.”

No HTTP served

Technical problem
No response on the server’s HTTP(S) port
Web server may be stopped/malfunctioning.
Firewalls may not allow connection.

The user’s perspective
The user enters the URL but gets a browser error message like “can’t establish a connection”.

Comments
The comment conveniently states the IP address and port number used in the HTTP request.

No URL called in macro

Technical problem
The sensor’s macro did not call a URL.

The user’s perspective
Browser state did not change after starting it.
HAR file is empty.

Comments
The macro may miss a URL GOTO command.
The macro may have failed before the URL GOTO was reached.

Empty page served

Technical problem
The HTTP response does not contain actual HTTP code

The user’s perspective
Browser shows an empty page instead of the expected content.

Comments
See Also What is a HAR File and what do I use it for?

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