How to Use the FILExt Site

When you click on a file type that Windows does not know how to open, a dialog appears asking if you want to search the Internet for a program. If you see this dialog, note carefully the full name of the file you clicked on. In particular, make a note of the characters that follow the last period in the file name.

Windows Can't Open Dialog

If you click that link you are taken to a Microsoft Web page that drops you into a Windows Live search. If you find FILExt as a listing in the returned search and click on it you come here. This all happens on the Web, not on your computer. FILExt is not in your computer.

If you are at this site you likely are looking for a program that works with a particular file extension. A file extension is nothing more than the last characters after the period in the name of a file (those characters you noted above). For a detailed explanation, examples, and a method of setting your system so that it shows file extensions please see this FAQ. To use the FILExt site to search for information...

  • The quickest way is to enter the file extension into the search box at the top left of each page and click on the Search button. If the extension is in the FILExt database a page will appear with all of the information FILExt has about the extension in question. If the extension is not in the database you will be directed to a page with suggestions on how to perform further research.
  • An alternate would be to use the alphabetical listings. Select the list that represents the first letter of the extension. Select the number list if the extension starts with a number (0...9)and the symbol list if it starts with a non-alphanumeric character ($#&@!()-{}'`_~). Scroll down the list until you find the extension of interest. If there, a summary line of information will appear by each instance of the extension. The extensions themselves will be linked to the same page that would have appeared had you searched as described above. Click on the extension to bring up that page.

Since there is no central registry that controls the use of file extensions you will often find more than one listing under a particular extension. FILExt is sorry, but if that is the case it will be up to you to determine which of them (if any of them) is the correct entry for the particular file you have. FILExt will try to help with notes but often it's not possible for FILExt to find all relevant information or that information has not been provided by submitters to the site. The millions of combinations make a complete database of all relevant information virtually impossible.

Once you have determined the type of file you are researching please seek further information from the Web site related to the program in question. Where known, relevant sites are linked on the extension listings. Please realize this is not a general support site. It is a catalog of file extensions, the programs that use those extensions, and links to those programs. So, basically, FILExt will try to help but you'll have to do some work as well.

Some general hints that apply when searching...

  • If the extension has a number in it (e.g., .S25) and no entry comes up for that try again using the number "1" or "01" (e.g., .S01). Often such files are part of a series and only the lowest five or ten entries in the series will be in the database.
  • If the extension is all numbers and no entry comes up try again with .000 or .001. Again, often such files are part of a series.
  • If the extension ends with an underscore (_) and no entry comes up for the particular extension it's likely that the file is part of an install set and is a compressed version of a file with the same first two characters (e.g., an .EXE file in a compressed install set becomes .EX_).

If you still don't find what you want...

Some estimate there are a million or so unique combinations of file extensions and program uses. While the FILExt site attempts to list the most popular of these, if you know anything about probability you will know there is some chance what you are looking for won't be here. If it isn't and you downloaded the file you are curious about then the best place to ask about it will be at the download site. If someone sent it to you, the easiest way to find out what it does is to ask the person who sent it to you. Finally, if are just found a file on your system are are simply curious, be careful. Messing with system files can lead to disaster.

As an altertive you can try to use TrID to analyze the file and see if it can determine what the file type is. TrID is a program that reads a file and compares its structure with a number of known structures. If a match is found you are presented with the alternatives. TrID is free and comes as a program you can load on your system or in an on-line version where you upload the file to their server for analysis there. [Note: With permission, FILExt uses the TrID data in its listings so TrID is best used to either narrow down your choices if a FILExt search results in multiple possibilities or if the file has no file extension (or might have the wrong one).


If you are technically oriented (or just plain curious) FILExt has another page with some suggestions about how to look inside a file. Sometimes by doing so you can get a hint about what created the file (e.g., some programs leave a copyright notice in their data files).

Finally, if you do find out information that's not here on the FILExt site please don't forget to come back and submit it to help others (use the link at the top of this page, if active).

Thank you and good luck.

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