GraFIX: Parsing low and high quality eye-tracking data

Please if you make use of our software, cite our paper:

Saez de Urabain, I.R., Johnson, M.H., Smith, T.J., (2014) GraFIX: A semiautomatic approach for parsing low- and high-quality eye-tracking data. Behavior Research Methods. doi:10.3758/s13428-014-0456-0 [Download article]


What is GraFIX?

GraFIX is a software and a method to detect fixations in low and high quality data, consisting of a two-step process in which eye-tracking data is initially parsed by using adaptive velocity-based algorithms, before it is hand-coded using the graphical interface, allowing accurate and rapid adjustments of the algorithms' outcome. GraFIX is released under the GPLv3 public license (

Some advanced features of GraFIX are listed as follows:

  • GraFIX is able to parse the data from any eye-tracker (e.g. Tobii, SMI or Eyelink eye-trackers) at any sampling frequency. 
  • It is a multiplatform application (Mac OS X, Windows and Linux), written in C++ and QT frameworks.
  • With a view to fit the data from subjects that present different levels of data-quality, the input parameters for the automatic algorithms (e.g. velocity threshold, interpolation latency) are adapted by the user on a participant basis.
  • Once the raw eye-tracking data (the x and y coordinates for the right and/or the left eyes) is loaded, it is smoothed by applying a bilateral filtering algorithm.
  • Segments of missing data can be interpolated.
  • Fixations are initially parsed with a velocity-based algorithm.
  • The post-hoc validation algorithms evaluate the output from the velocity-based algorithms and fix and/or remove a number of artifactual fixations.
  • Once the fixations have been automatically calculated, the user can use GraFIX graphical tools to examine and manipulate them in order to fix the algorithms’ outcome. Even the most accurate algorithms may generate a number of artifactual fixations that can corrupt the validity of the experimental results.
  • GraFIX is able to visualize and replay the eye-movements data in various ways.
  • It provides data quality measurements.
  • It includes pupil-dilation.