Two Norwegian students, Arne Georg Gleditsch and Per Kristian Gjermshus, curious about Linux architecture, began writing a small program displaying its files through a web-browser and showing variables usages after a click on the name.

Time passing, fans joined the development team to give code more maturity; however their number never exceeded ten.

MXR was forked in order to meet the needs of Mozilla development, namely code navigation of a mixed C++ and JavaScript codebase.

After years of MXR use, Mozilla began work on a new tool with a focus on better static analysis and a dynamic Ajax UI.

Afterwards, all is needed is to launch a web browser with an URL corresponding to the source code and navigate across files through the hyperlinks associated to identifiers.

To work around the indexing phase limitations, any character sequence may be (full text) searched at the cost of an extensive source files traversal.