Content Rules and the Joy of Regular Expressions

Posted on


Regular Expressions (commonly called ‘regexes’ or ‘a regex’) are simple … right? To the initiated, a regex provides unrivalled clarity and succinctness of thought and expression. To the rest of us, it’s tough to learn and the syntax is mystifying; but, thankfully, a myriad of free tools exist to help us turn frustration into joy. “Well, isn’t all that is great!”, you say! Are there any specific tools that I can leverage to help me specifically with creating regexes for LoadMaster Content Rules? Can you make that a more joyous experience?

I am delighted to announce the availability of the Kemp LoadMaster Content Rule Builder tool. LoadMaster simplifies traffic steering and modification by using content rules which are based on regular expression syntax. The content rules engine can add/remove/edit headers, rewrite URLs, rewrite HTTP payload bodies, and content matching based off headers and/or URIs. Regexes are used in content rules primarily to perform pattern matching on client request and server responses to select specific streams for specific actions – such as header modification or traffic direction.

Content rule builder

The new Content Rule Builder provides a graphical way to build the most common content rule constructs used on the LoadMaster. It doesn’t cover the entire gamut of regex use cases, but does provide solutions to the most common use cases,including:

  • Match on host/domain or URL/path
  • Change host/domain or URL/path
  • Change naked domains to FQDNs (e.g., to
  • Change 302 redirects to another location
  • Add and remove ports from URLs

The output from the Content Rule Builder can be applied directly to the LoadMaster via RESTful or PowerShell API or from the Content Rule creation page within the LoadMaster UI.

A video is available here that demonstrates how to use this tool; but, if you are ready to go, please click here to start using the Content Rule Builder and speed your time to custom application delivery!

Posted on

David O'Connor

David O’Connor is a Product Manager in Kemp working in Limerick, Ireland. He holds a bachelor’s degree in Computer Engineering from University of Limerick. David has a telecoms background with previous roles in development, customer support and presales with a focus on product-market fit and creating tech products that customers love.