EDF to ASCII Conversion / EDF2ASC
For some data analysis pipelines it may be appropriate to convert the EDF Files to ASCII, so that the data can be imported into other software such as R, Python or Matlab for further processing. Please note that EDF files can also be read into Matlab directly via the edfmex tool - as described in the Getting Started with Data Analysis in Matlab thread. EDF files can also be read into R directly via eyelinkReader, as described in the Getting Started with Data Analysis in R thread.

It is also worth noting that a Sample Report generated by Data Viewer often provides a far richer and more manageable source of sample and event level ASCII data for import into other software compared to the output of a straight ASCII conversion using the tools below. In addition to columns containing the basic x,y gaze data, Data Viewer Sample Reports can output columns of 1s and 0s indicating whether each sample was in a saccade or blink, columns indicating which Interest Area each sample was in, and columns containing trial IDs and variable values. For examples of how Data Viewer's rich Sample Reports can be further processed, please see the Microsaccade Analysis and Smooth Pursuit Analysis threads:

EDF Converters:
If you need to convert EDF files to ASCII you can use EDF2ASC, an EDF to ASCII converter which is provided as both a command line tool and a GUI app, for Windows, macOS and Linux. 

For macOS and Linux both the command line and GUI versions of EDF2ASC are bundled with the EyeLink Developer's Kit. For Windows, the command line version is bundled with the Developer's Kit, but the GUI version (VisualEDF2ASC) is bundled with Data Viewer.

EyeLink Developer's Kit Download 
EyeLink Data Viewer Download  (for Windows GUI version of EDF2ASC)

Both the command line and GUI versions of EDF2ASC allow you to output Samples and/or Events, as well as other useful data such as velocity and resolution (pixel per degree values). They also allow EDF Files to be converted in "Failsafe Mode" which can allow some corrupted EDFs to be converted. 

The GUI versions are supplied with help files that detail their functionality.  Simply typing edf2asc without any parameters will list the various flags and parameters for the command line versions.

For a detailed introduction to EyeLink data, and the contents of EyeLink Data Files (EDF Files) that have been converted to ASCII, please see the following thread:

An Introduction to EyeLink Data (EDF Files)