Abstract: A method, apparatus, and computer program product for measuring inline internet ad performance for third-party ad serving. The method comprises receiving an original third-party internet ad and recoding the original third-party internet ad for producing a recoded third-party internet ad where the recoded third-party internet ad comprises ad instrumentation code. In real-time, as the internet ad is composited and rendered, the instrumentation code measures the response latency of the server or servers in the third-party network using the ad instrumentation code. In some cases, the original third-party internet ad comprises ad code using a markup language such as HTML language, and/or JavaScript language (e.g. in ad code segments). The recoding comprises recoding an ad code segment of the ad by transforming the ad code segment into a JavaScript literal, which in exemplary embodiments includes emitting a specialized document.write( ) call.