Search, XChange and XChangeCL can only operate correctly on ANSI text files. These are sometimes known as flat files because they do not contain any text formatting information.

Search, XChange and XChangeCL will not operate correctly on word processor files, such as those produced by Microsoft Word, nor on spreadsheet files, such as those produced by Microsoft Excel. You can, of course, first export the contents to a text or comma-separated-value (CSV) file which can then be processed correctly.

As a rough rule of thumb, if you can open and save a file using Windows Notepad without destroying or corrupting its contents, then it is suitable for processing with Search, XChange or XChangeCL.

Note: Since the advent of Windows XP and later, this rule of thumb needs an additional condition, as later versions of Notepad can also operate on Unicode format files whilst Search, XChange and XChangeCL cannot. If you open the file in Notepad, select the "File" -> "Save As" menu option, and the default encoding is ANSI then Search, XChange and XChangeCL should have no problem. If the default encoding is Unicode, they won't be able to process the file.

Some common file extensions for text files are:

text file
log file
comma-separated-value file. May often be exported by spreadsheets.
htm, html, shm, shtm, shtml, css, js, xml, xls, asp
web pages, style sheets and javascript code.
pas, dpr, dpk, dof, cfg, dsk, dfm
Pascal/Delphi source code and project files.
c, cpp, h, hpp
C and C++ source code.
Java source code.
frm, bas, cls, ctl, vbp, vbw
Microsoft Visual Basic source code.
DOS or Windows batch file.
Application configuration settings.
sln, cs, csproj, aspx, asax, ascx, config, webinfo
Microsoft .NET, C# and ASP.NET pages.

This is by no means an exhaustive list. There are many, many other file extensions used for text files.