PRTG Manual: HTTP Advanced Sensor

The HTTP Advanced sensor monitors the source code of a web page using HTTP. It supports authentication, content checks, and other advanced parameters.

i_round_blueThe monitored content size is uncompressed.

HTTP Advanced Sensor

HTTP Advanced 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 Geavanceerd

French: HTTP avancé

German: HTTP (Erweitert)

Japanese: HTTP アドバンスト

Portuguese: HTTP (avançado)

Russian: HTTP (Расширенный)

Simplified Chinese: HTTP 高级

Spanish: HTTP (avanzado)

Remarks

This sensor does not support Secure Remote Password (SRP) ciphers. If you need to use SRP ciphers, use the Compatibility engine in the sensor settings.

This sensor does not support HTTP compression. If you need to use HTTP compression, use the Compatibility engine in the sensor settings.

This sensor supports smart URL replacement.

This sensor supports the IPv6 protocol.

This sensor has a medium performance impact.

Bandwidth monitoring of fast internet connections may be inaccurate.

See the Knowledge Base: Which user agent should I use in the HTTP Advanced sensor's settings?

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.

Monitoring Engine

Monitoring Engine

Monitoring Engine

Setting

Description

Monitoring Engine

Choose the monitoring engine that the sensor uses:

Default engine (recommended): Use the default monitoring engine.

Compatibility engine: Execute an external executable program. Use this method as an alternative for websites that do not work with the default monitoring engine.
i_round_blueThis method needs more resources but it can be helpful in some cases.
i_round_blueIf you select the compatibility mode, the options for the SSL method are different. You can also check for trusted certificates. See below.
i_round_redSmart URL Replacement does not work with the compatibility mode, so this sensor does not automatically use the IP Address/DNS Name of the parent device.

SSL/TLS Method

This option is only visible if you select Compatibility engine above. Choose from:

SSLv3

TLS 1.0, TLS 1.1, TLS 1.2

SSLv3, TLS 1.0, TLS 1.1, TLS 1.2 (default)

Check SSL Certificates

This option is only visible if you select Compatibility engine above. Specify if the sensor checks the certificate of the URL:

Do not check certificates (default): Do not check the certificates of the web pages.

Check if certificates are trusted: Check the certificates of the web pages. If the certificate of the server is not trusted, the sensor shows the Down status and displays a corresponding message.

Advanced Sensor Data

Advanced Sensor Data

Advanced Sensor Data

Setting

Description

HTTP Version

Define the HTTP version that the sensor uses when it connects to the target URL:

HTTP 1.0: Use HTTP version 1.0.

HTTP 1.1: Use HTTP version 1.1.

User Agent

Choose which user agent string the sensor sends when it connects to the target URL:

Use the default string: Do not enter a specific user agent and use the default string. Usually, this is Mozilla/5.0 (compatible; PRTG Network Monitor (www.paessler.com); Windows).

Use a custom string: Use a custom user agent. Define the custom user agent below.

Custom User Agent

This setting is only visible if you enable Use a custom string above. Enter the string that the sensor uses as the user agent when it connects to the target URL.

HTTP Headers

Define if you want to send custom HTTP headers to the target URL:

Do not use custom HTTP headers: Do not use custom HTTP headers.

Use custom HTTP headers: Use custom headers. Define below.

Custom HTTP Headers

This setting is only visible if you enable Use custom HTTP headers above. Enter a list of custom HTTP headers and values that you want to transmit to the URL, each pair in one line. The syntax of a header-value pair is header1:value1

i_round_redThe sensor does not support the header field names user-agent, content-length, and host.

i_round_redEnsure that the HTTP header statement is valid. Otherwise, the sensor request cannot be successful.

If Content Changes

Define what the sensor does if the content of the web page (element) changes:

Ignore changes: Do nothing.

Trigger 'change' notification: Send an internal message that indicates that the web page content has changed. In combination with a change trigger, you can use this mechanism to trigger a notification whenever the web page content changes.

Require Keyword

Define if the sensor checks the result at the URL for keywords:

Do not check for keyword (default): Do not search for keywords in the result.

Set sensor to warning status if keyword is missing: Check if a keyword exists in the result. If it exists, set the sensor to the Warning status.

Set sensor to down status if keyword is missing: Check if a keyword exists in the result. If it exists, set the sensor to the Down status.

i_round_blueThe content check is only intended for HTML websites and might not work with other target URLs. For example, binary files are not supported.

i_round_redThis sensor loads the source code at the URL. If you set up a content check, only this source code is checked for the keywords. The code is not necessarily identical to the code used to display the page when opening the same URL in a web browser. This is because a reload might be configured or certain information might be inserted after loading, for example, via JavaScript.

i_round_redPRTG does not follow links to embedded objects nor does it execute scripts. Only the first page at the URL is loaded and checked against the expressions configured.

Response Must Include

This setting is only visible if you select Set sensor to warning status if keyword is missing or Set sensor to down status if keyword is missing above. Define the search string that must be part of the source code at the URL. You can enter a simple string in plain text or a regular expression (regex).

i_round_blueIf the source code does not include the search pattern, the sensor shows the status defined above.

i_round_redThe search string must be case sensitive.

Search Method

Define the method with which you want to provide the search string:

Simple string search: Search for a simple string in plain text.

i_round_blueThe characters * and ? work as placeholders. * stands for no number or any number of characters and ? stands for exactly one character. You cannot change this behavior. The literal search for these characters is only possible with a regex.
i_round_blueYou can also search for HTML tags.

Regular expression: Search with a regex.

i_round_bluePRTG supports Perl Compatible Regular Expression (PCRE) regex. For more details, see section Regular Expressions.

Exclude Keyword

Define if the sensor checks the result at the URL for keywords:

Do not check for keyword (default): Do not search for keywords in the result.

Set sensor to warning status if keyword is found: Check if a keyword exists in the result. If it exists, set the sensor to the Warning status.

Set sensor to down status if keyword is found: Check if a keyword exists in the result. If it exists, set the sensor to the Down status.

i_round_blueThe content check is only intended for HTML websites and might not work with other target URLs. For example, binary files are not supported.

Response Must Not Include

This setting is only visible if you selectSet sensor to warning status if keyword is found or Set sensor to down status if keyword is found above. Define the search string that must not be part of the source code at the specified URL. You can enter a simple string in plain text or a regular expression.

i_round_redThe search string must be case sensitive.

i_round_blueIf the data does include this string, the sensor shows the status defined above.

Search Method

Define the method with which you want to provide the search string:

Simple string search: Search for a simple string in plain text.

i_round_blueThe characters * and ? work as placeholders. * stands for no number or any number of characters and ? stands for exactly one character. You cannot change this behavior. The literal search for these characters is only possible with a regex.
i_round_blueYou can also search for HTML tags.

Regular expression: Search with a regex.

i_round_bluePRTG supports Perl Compatible Regular Expression (PCRE) regex. For more details, see section Regular Expressions.

Download Limit (KB)

Enter the maximum amount of data (in kilobytes) that is transferred per request.

i_round_redIf you set content checks, be aware that they might be incomplete because only the content downloaded up to this limit is checked for search expressions.

Result Handling

Define what the sensor does with the data loaded at the URL:

Discard result: Do not store the sensor result.

Store result: Store the last result of the requested data in the \Logs\sensors subfolder of the PRTG data directory on the probe system. The file names are Result of Sensor [ID].txt, Result of Sensor [ID]-A.txt, and Result of Sensor [ID].Data.txt. This setting is for debugging purposes, especially in combination with content checks. PRTG overwrites these files with each scanning interval.

i_round_blueFor debugging, select Store result to write the source code file to disk and to look up what exactly PRTG gets when it calls the URL. If the URL does not point to a web page but to a binary file, for example, to an image, you usually do not check for content.

i_podThis option is not available when the sensor runs on the hosted probe of a PRTG Hosted Monitor instance.

i_round_blueIn a cluster, PRTG stores the result in the PRTG data directory of the master node.

Authentication

Authentication

Authentication

Setting

Description

Authentication

Define if authentication is necessary on the web page:

Web page does not need authentication

Web page needs authentication

User Name

If the proxy requires authentication, enter the user name for the proxy login.

i_round_redOnly basic authentication is available. Enter a string.

Password

This setting is only visible if you select Web page needs authentication above. Enter a password.

Authentication Method

This setting is only visible if you select Web page needs authentication above. Select the authentication method that the URL uses:

HTTP authentication: Use simple HTTP authentication.
i_round_redThis authentication method transmits credentials as plain text.

NT LAN Manager authentication: Use the Microsoft NT LAN Manager (NTLM) protocol for authentication.

Digest access authentication: Use digest access authentication. This applies a hash function to the password, which is safer than HTTP authentication.

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.

Channel Unit Configuration

i_round_blueWhich channel units are available depends on the sensor type and the available parameters. If no configurable channels are available, this field shows No configurable channels.

Channel Unit Configuration

Channel Unit Configuration

i_square_cyanFor more information, see section Root Group Settings, section Channel Unit Configuration.

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

Bytes Received

The received bytes

Download Bandwidth

The download speed in bytes per second

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 in milliseconds (msec)

i_round_blueThis channel is the primary channel by default.

Time To First Byte

The time to the first byte in msec

More

i_square_blueKNOWLEDGE BASE

Which user agent should I use in the HTTP Advanced sensor's settings?

https://kb.paessler.com/en/topic/30593

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

Why do my HTTP Advanced sensors differ in the bytes received value?

https://kb.paessler.com/en/topic/78778

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

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