PRTG Manual: HTTP Webpage Sensor
The HTTP Webpage sensor monitors the full page load time of a webpage in Google Chrome, including assets such as images. In the background, it opens the webpage in a headless browser instance to perform the measurement. It does not follow links.
This sensor can generate a considerable amount of internet traffic if you use it with a short scanning interval.
HTTP Webpage Sensor
For a detailed list and descriptions of the channels that this sensor can show, see section Channel List.
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Consider the following remarks and requirements for this sensor:
Remark |
Description |
|---|---|
Performance impact |
This sensor has a high performance impact. |
Browser |
This sensor requires that Google Chrome is installed on the probe system and available for all users. If you use this sensor in a cluster, Google Chrome must be installed on all cluster nodes.
|
Smart URL replacement |
This sensor supports smart URL replacement. |
IPv6 |
This sensor supports IPv6. |
Scanning interval |
This sensor has a fixed minimum scanning interval for performance reasons. You cannot use a shorter scanning interval. Consequently, shorter scanning intervals in the Monitoring settings are not available for this sensor.
|
Limits |
This sensor has predefined limits for one or several metrics. |
Basic Sensor Settings
The sensor has the following default tags that are automatically predefined in the sensor's settings when you add the sensor:
- browser
- http
- httpwebsensor
- performance
- webpagesensor
For more information about basic sensor settings, see section Sensor Settings.
Specific Sensor Settings
Setting |
Description |
|---|---|
URL |
Enter the full URL of the webpage that you want to monitor. The default URL is https://%host/. The sensor resolves %host as the parent device's IP address or DNS name. If you enter an absolute URL, the sensor uses this address independently of the IP Address/DNS Name setting of the parent device.
|
Remote Debugging Port |
Select the Chrome DevTools Protocol (CDP) port that this sensor uses:
Each sensor instance must use a unique unoccupied port. If multiple sensors use the same port, scan failures occur when their scans overlap. |
Custom Debugging Port |
This setting is only visible if you select Remote Debugging Port above. Enter the port number for the CDP debugging interface. PRTG supports port numbers 1 - 65535. |
Page Load Timeout (Sec.) |
Enter the maximum allowed time in seconds for the request. The check request includes Google Chrome startup, CDP connection, and page load. The default timeout is 20 seconds. The maximum timeout is 300 seconds (5 minutes). |
Certificate Validation |
Select whether the sensor validates the webpage certificate:
|
Viewport Size |
Select the viewport size that Google Chrome uses to render the page:
|
Sensor Display
Setting |
Description |
|---|---|
Primary Channel |
Select a channel from the list to define it as the primary channel. In the device tree, PRTG displays the last value of the primary channel below the sensor's name. The available options depend on what channels are available for this sensor.
|
Graph Type |
Define how this sensor shows different channels:
|
Stack Unit |
This setting is only visible if you select Stack channels on top of each other above. Select a unit from the list. PRTG stacks all channels with this unit on top of each other. By default, you cannot exclude single channels from stacking if they use the selected unit. However, there is an advanced procedure to do so. |
Debug Options
Setting |
Description |
|---|---|
Result Handling |
Define what PRTG does with the sensor result:
|
This option is not available when the sensor runs on the hosted probe of a PRTG Hosted Monitor instance.By default, all of these settings are inherited from objects that are higher in the hierarchy. We recommend that you change them centrally in the root group settings if necessary. To change a setting for this object only, click 
under the corresponding setting name to disable the inheritance and to display its options.
For more information, see section Inheritance of Settings.
To find a usable Google Chrome installation, the sensor searches for the Google Chrome executable. The sensor uses the first executable it finds in the following order:
- Environment variable: The sensor checks the system environment variables for PRTG_BROWSER_PATH. This variable must contain the full path to the Google Chrome executable file, for example C:\Program Files\Google\Chrome\Application\chrome.exe.
- Windows registry: On Windows systems, the sensor checks the Windows registry for the variable BrowserPath. This variable must contain the full path to the Google Chrome executable file. The sensor looks in the following registry keys:
- HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Paessler\PRTG Network Monitor\Probe
- HKEY_LOCAL_MACHINE\SOFTWARE\Paessler\PRTG Network Monitor\Probe
- Default browser: The sensor checks the default browser of the PRTG probe system.
- Known default paths: The sensor checks the known standard paths for Google Chrome:
- Windows
- %ProgramFiles%\Google\Chrome\Application\chrome.exe
- %ProgramFiles(x86)%\Google\Chrome\Application\chrome.exe
- %LocalAppData%\Google\Chrome\Application\chrome.exe
- Linux
- /usr/bin/google-chrome
- /usr/bin/google-chrome-stable
- /usr/bin/chromium
- /usr/bin/chromium-browser
- /opt/google/chrome/chrome
- Windows
If the sensor cannot find a valid Google Chrome installation, it shows the Down status.
Instead of entering a complete address in the URL field of an HTTP sensor, you can enter the protocol followed by a colon and three forward slashes (this means that you can enter either http:/// or https:///, or even a simple forward slash / as the equivalent for http:///). PRTG automatically fills in the parent device's IP Address/DNS Name in front of the third forward slash.
Whether this results in a valid URL or not depends on the IP address or Domain Name System (DNS) name of the parent device. In combination with cloning devices, you can use smart URL replacement to create many similar devices.
For example, if you create a device with the DNS name www.example.com and you add an HTTP sensor to it, you can provide values in the following ways:
- If you enter https:/// in the URL field, PRTG automatically creates the URL https://www.example.com/
- If you enter /help in the URL field, PRTG automatically creates and monitors the URL http://www.example.com/help
- It is also possible to provide a port number in the URL field. It is taken over by the device's DNS name and is internally added, for example, http://:8080/
Smart URL replacement does not work for sensors that run on the probe device.
Which channels the sensor actually shows might depend on the target device, the available components, and the sensor setup.
Channel |
Description |
|---|---|
Downtime |
In the channel table on the Overview tab, this channel never shows any values. PRTG uses this channel in graphs and reports to show the amount of time in which the sensor was in the Down status. |
Page Load Time |
The loading time of the webpage
|
KNOWLEDGE BASE
My HTTP sensors don't work. What can I do?
What security features does PRTG include?
