PRTG Manual: HTTP Sensor
The HTTP sensor monitors a web server using HTTP.
You can use this sensor to monitor if a website or a specific website element is reachable.
For a detailed list and descriptions of the channels that this sensor can show, see section Channel List.
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- This sensor does not support Secure Remote Password (SRP) ciphers.
- This sensor supports smart URL replacement.
- This sensor supports IPv6.
- This sensor has a low performance impact.
- Knowledge Base: Which HTTP status code leads to which HTTP sensor status?
Setting |
Description |
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Sensor Name |
Enter a name to identify the sensor. By default, PRTG shows this name in the device tree, as well as in alarms, logs, notifications, reports, maps, libraries, and tickets.
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Parent Tags |
The tags that the sensor inherits from its parent device, parent group, and parent probe.
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Tags |
Enter one or more tags. Confirm each tag with the Spacebar key, a comma, or the Enter key. You can use tags to group objects and use tag-filtered views later on. Tags are not case-sensitive. Tags are automatically inherited.
The sensor has the following default tags that are automatically predefined in the sensor's settings when you add the sensor:
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Priority |
Select a priority for the sensor. This setting determines the position of the sensor in lists. The highest priority is at the top of a list. Choose from the lowest priority ( |
Setting |
Description |
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Timeout (Sec.) |
Enter a timeout in seconds for the request. Enter an integer. The maximum timeout value is 900 seconds (15 minutes).
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URL |
Enter the URL that the sensor connects to. If you enter an absolute URL, the sensor uses this address independently of the IP Address/DNS Name setting of the parent device. You can enter the URL of a web page (to measure the loading time of the page's source code), or enter the URL of an image or of a page asset to measure this element's availability and loading time.
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Request Method |
Select an HTTP request method to determine how the sensor requests the URL:
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Postdata |
This setting is only visible if you select POST above. Enter the data part for the POST request.
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Content Type |
This setting is only visible if you select POST above. Define the content type of the POST request:
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Custom Content Type |
This setting is only visible if you select Custom above. Define the custom content type, for example, XML, JavaScript Object Notation (JSON), or HTTP. |
Server Name Indication |
The Server Name Indication (SNI) that the sensor automatically determines from the host address of the parent device or from the target URL of the sensor.
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SNI Inheritance |
Define if you want to inherit the SNI from the parent device:
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Setting |
Description |
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Primary Channel |
Select a channel from the list to define it as the primary channel. In the device tree, the last value of the primary channel is always displayed below the sensor's name. The available options depend on what channels are available for this sensor.
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Graph Type |
Define how different channels are shown for this sensor:
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Stack Unit |
This setting is only visible if you select Stack channels on top of each other above. Select a unit from the list. All channels with this unit are stacked 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. |
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.
The proxy settings determine how a sensor connects to a URL. You can enter data for an HTTP proxy server that sensors use when they connect via HTTP or HTTPS.
This setting only applies to sensors and how they monitor. For more information on how to change the proxy settings for the PRTG core server, see section Core & Probes.
For more information, see section Root Group Settings, section Proxy Settings.
For more information, see section Root Group Settings, section Scanning Interval.
Schedules, Dependencies, and Maintenance Window
You cannot interrupt the inheritance for schedules, dependencies, and maintenance windows. The corresponding settings from the parent objects are always active. However, you can define additional schedules, dependencies, and maintenance windows. They are active at the same time as the parent objects' settings.
For more information, see section Root Group Settings, section Schedules, Dependencies, and Maintenance Window (default).
For more information, see section Root Group Settings, section Access Rights.
Instead of entering a complete address in the URL field of an HTTP sensor, you can only 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 monitor 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 |
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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 |
Loading Time |
The web page or element loading time
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KNOWLEDGE BASE
My HTTP sensors fail to monitor websites which use SNI. What can I do?
Which HTTP status code leads to which HTTP sensor status?
What security features does PRTG include?
My HTTP sensors don't work. What can I do?