The purpose of ESI is to tackle the problem of web infrastructure scaling.
To overcome this problem a group of companies (Akamai, Art Technology Group, BEA Systems, Circadence Corporation, Digital Island, Inc., Interwoven, Inc., Open Market, whose ESI-related technology is now owned by FatWire Software, Oracle Corporation and Vignette Corporation) developed the ESI specification and submitted it to the W3C for approval.
ESI Language Specification 1.0 was submitted to the World Wide Web Consortium (W3C) for approval in August 2001.
[4] ESI element tags are inserted into HTML or other text based content during creation.
The XML based ESI tags indicate to the edge-side processing agent the action that needs to be taken to complete the page's assembly.