PRTG Manual: HTTP Sensor

The HTTP sensor monitors a web server using HTTP.

i_round_blueYou can use this sensor to monitor if a website or a specific website element is reachable.

HTTP Sensor

HTTP Sensor

i_square_cyanFor a detailed list and descriptions of the channels that this sensor can show, see section Channel List.

Sensor in Other Languages

Dutch: HTTP

French: HTTP

German: HTTP

Japanese: HTTP

Portuguese: HTTP

Russian: HTTP

Simplified Chinese: HTTP

Spanish: HTTP

Remarks

This sensor does not support Secure Remote Password (SRP) ciphers.

This sensor supports smart URL replacement.

This sensor supports the IPv6 protocol.

This sensor has a low performance impact.

See the Knowledge Base: My HTTP sensors fail to monitor websites which use SNI. What can I do?

See the Knowledge Base: Which HTTP status code leads to which HTTP sensor status?

Add Sensor

The Add Sensor dialog appears when you manually add a new sensor to a device. It only shows the settings that are required to create the sensor. You can change nearly all settings on the sensor's Settings tab after creation.

Basic Sensor Settings

Click the Settings tab of a sensor to change its settings.

Basic Sensor Settings

Basic Sensor Settings

Setting

Description

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.

i_round_blueIf the name contains angle brackets (<>), PRTG replaces them with braces ({}) for security reasons. For more information, see the Knowledge Base: What security features does PRTG include?

Parent Tags

Shows tags that the sensor inherits from its parent device, parent group, and parent probe.

i_round_blueThis setting is for your information only. You cannot change it.

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.

i_round_blueIt is not possible to enter tags with a leading plus (+) or minus (-) sign, nor tags with parentheses (()) or angle brackets (<>).

i_round_blueFor performance reasons, it can take some minutes until you can filter for new tags that you added.

The sensor has the following default tags that are automatically predefined in the sensor's settings when you add the sensor:

httpsensor

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 (i_priority_1) to the highest priority (i_priority_5).

i_round_blueUsually, a sensor connects to the IP Address/DNS Name of the parent device. See the device settings for details. For some sensors, you can explicitly define the monitoring target in the sensor settings.

HTTP Specific

HTTP Specific

HTTP Specific

Setting

Description

Timeout (Sec.)

Enter a timeout in seconds for the request. Enter an integer. The maximum timeout value is 900 seconds (15 minutes).

i_round_blueIf the reply takes longer than this value, the sensor cancels the request and shows a corresponding error message.

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.

i_round_redThe URL must be URL encoded.

i_round_redIf you monitor an image or a page asset, this can create a high amount of memory load. We recommend that the size of the elements that you want to monitor does not exceed 200 MB.

i_square_cyanPRTG uses a smart URL replacement with which you can use the parent device's IP address or Domain Name System (DNS) name setting as part of the URL. For more information, see section Smart URL Replacement.

Request Method

Select an HTTP request method to determine how the sensor requests the URL:

GET: Directly request the website.
i_round_blueWe recommend that you use this setting for a simple check of the web page.

POST: Send post form data to the URL.
i_round_redIf you select this setting, you must enter the data in the Postdata field below.

HEAD: Only request the HTTP header from the server without the actual web page.
i_round_blueAlthough this saves bandwidth because it transfers less data, we do not recommended that you use this. This is because the measured request time is not the one that your users experience and you might not be notified of slow results or timeouts.

Postdata

This setting is only visible if you select POST above. Enter the data part for the POST request.

i_round_redNo Extensible Markup Language (XML) is allowed here.

Content Type

This setting is only visible if you select POST above. Define the content type of the POST request:

Default (application/x-www-form-urlencoded): Use the default content type to encode the form data set for submission to the server.

Custom: Use a custom content type. Enter the content type below.

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

Shows 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.
i_round_redThe SNI must be a fully qualified domain name (FQDN). Make sure that it matches the configuration of the target server.

i_square_cyanFor details, see the Knowledge Base: My HTTP sensors fail to monitor websites which use SNI. What can I do?

i_round_blueThis sensor implicitly supports SNI, an extension to the Transport Layer Security (TLS) protocol.

i_round_bluePRTG shows this value for reference purposes only. If you need to change this value, add the sensor anew.

SNI Inheritance

Define if you want to inherit the SNI from the parent device:

Inherit SNI from parent device: Determine the SNI from the host address of the parent device.

Do not inherit SNI from parent device: Determine the SNI from the target URL as defined in the settings of this sensor.

Sensor Display

Sensor Display

Sensor Display

Setting

Description

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.

i_round_blueYou can set a different primary channel later by clicking b_channel_primary below a channel gauge on the sensor's Overview tab.

Graph Type

Define how different channels are shown for this sensor:

Show channels independently (default): Show a graph for each channel.

Stack channels on top of each other: Stack channels on top of each other to create a multi-channel graph. This generates a graph that visualizes the different components of your total traffic.
i_round_redYou cannot use this option in combination with manual Vertical Axis Scaling (available in the channel settings).

Stack Unit

This setting is only visible if you enable Stack channels on top of each other as Graph Type. 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.

Inherited Settings

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 b_inherited_enabled under the corresponding setting name to disable the inheritance and to display its options.

i_square_cyanFor more information, see section Inheritance of Settings.

Proxy Settings for HTTP Sensors

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.

i_round_blueThis setting only applies to HTTP sensors and how they monitor. To change the proxy settings for the PRTG core server, see section Core & Probes.

Proxy Settings for HTTP Sensors

Proxy Settings for HTTP Sensors

i_square_cyanFor more information, see section Root Group Settings, section Proxy Settings for HTTP Sensors.

Scanning Interval

Scanning Interval

Scanning Interval

i_square_cyanFor more information, see section Root Group Settings, section Scanning Interval.

Schedules, Dependencies, and Maintenance Window

i_round_blueYou 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.

Schedules, Dependencies, and Maintenance Window

Schedules, Dependencies, and Maintenance Window

i_square_cyanFor more information, see section Root Group Settings, section Schedules, Dependencies, and Maintenance Window.

Access Rights

Access Rights

Access Rights

i_square_cyanFor more information, see section Root Group Settings, section Access Rights.

Smart URL Replacement

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/

i_round_redSmart URL replacement does not work for sensors that run on the probe device.

Channel List

i_round_blueWhich 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

Loading Time

The loading time of the web page or element in milliseconds (msec)

i_round_blueThis channel is the primary channel by default.

More

i_square_blueKNOWLEDGE BASE

My HTTP sensors fail to monitor websites which use SNI. What can I do?

https://kb.paessler.com/en/topic/67398

Which HTTP status code leads to which HTTP sensor status?

https://kb.paessler.com/en/topic/65731

What security features does PRTG include?

https://kb.paessler.com/en/topic/61108

My HTTP sensors don't work. What can I do?

https://kb.paessler.com/en/topic/85284