SET File Documentation
Summary
A SET (Settings File) stores configuration or preferences for a program, written in whatever binary or text layout that program chose, so there is no single .set format. Many unrelated applications use the extension: AutoCAD, Corel Painter, games, EEGLAB datasets in neuroscience, and the old Microsoft Backup tool all wrote .set files for their own purposes. You normally do not open a .set by hand; the application that created it loads it automatically. To tell what one really is, note which program and folder it came from, or inspect its header in a text or hex editor.
Technical details
| Feature | Value |
|---|---|
| Full name | Settings File (application-defined) |
| File extension | .set |
| MIME type | application/octet-stream (no registered type) |
| Format type | Generic settings/preferences; layout defined by the creating app |
| Contents | Program options, saved configuration, or app-specific data |
| Encoding | Varies — plain text or proprietary binary, per app |
| Magic number | None — no common signature (identify by source app) |
| Common creators | AutoCAD, Corel Painter, Nikon Capture, games, EEGLAB, Microsoft Backup |
| Typical location | Inside the app’s install or user-profile folder |
| Opened by | The originating program (usually loaded automatically) |
| Safe to delete? | Usually — the app often recreates defaults (back up first) |
| Open standard | No (there is no single .set specification) |
| Related extensions | .ini, .cfg, .dat, .bak |
What is a SET file?
A .set file is a settings or configuration file: data a program saves to remember its options, and reloads the next time it runs. The key thing to understand is that .set is not one format. It is one of the most heavily reused extensions in existence, claimed independently by many unrelated programs, each of which defines its own internal layout. There is no shared specification, no registered MIME type, and no single magic number. What a particular .set file is depends entirely on the application that wrote it.
Because of that, the useful questions about a .set are practical ones: which program created this file, is it text or binary inside, is it safe to delete or edit, and how do I open it if I need to. The sections below answer those, rather than pretending there is a byte structure to document.
Identifying which program created it
Since the meaning is program-specific, the reliable way to know what a .set is comes from its context, not its extension. Two clues do most of the work: where the file lives, and what its first bytes look like. A .set sitting in an application’s install directory or its per-user settings folder almost certainly belongs to that application. Opening the file in a text editor or a hex viewer then tells you whether it is human-readable configuration (keys and values you can recognise) or an opaque binary blob. Some of the programs that use the extension:
| Program / use | What its .set holds |
|---|---|
| AutoCAD, Corel Painter, Nikon Capture | saved preferences / option sets |
| Various games | saved configuration or options |
| EEGLAB (MATLAB toolbox) | an EEG dataset (paired with a .fdt data file) |
| Sibelius | an instrument sound set |
| Microsoft Backup (MS-DOS 6 / Win9x) | a legacy backup-job definition |
The list is not exhaustive, which is the point: an unfamiliar .set should be identified before you assume what it does.
Whether a SET file is safe to delete or edit
A .set is data, not a program, so it does not run by itself and poses no direct malware risk. The realistic hazard is breakage, not security. If the file holds a program’s settings, deleting it usually just resets that program’s options, and many applications simply recreate a default .set on the next launch. Editing one by hand can corrupt those options if you change a value the program does not expect. The sensible rule is to back up the file before deleting or editing it, and to let the owning application manage it wherever possible. For a paired dataset such as an EEGLAB .set, keep it together with its companion .fdt file, since one is meaningless without the other.
The legacy “backup file set” meaning
One specific, historical meaning is worth naming because it is where the extension’s name comes from. Microsoft Backup, the simple utility bundled with MS-DOS 6 and Windows 9x (MSBACKUP and MWBACKUP), wrote a .set file to record the definition of a backup job: which drives, folders and files to include, and the options chosen. Crucially, the .set was the job definition, not the backed-up data, which those tools stored separately. Those utilities are long obsolete; modern Windows backup uses different mechanisms entirely. So a genuine Microsoft Backup .set is essentially a historical artefact today, and restoring one requires the same era’s tool, typically inside a virtual machine running the original OS. For most people encountering a .set now, this backup meaning is not the relevant one; a program’s settings file is far more likely.
Frequently asked questions
How do I open a SET file?
Figure out which program created it, usually from the folder it lives in, and let that program load it; .set files are normally read automatically, not opened by hand. To inspect an unknown one, open it in a text editor or hex editor to see whether it is readable settings or binary data, which also helps identify its source.
Can I delete a SET file?
If it is a program’s settings file, deleting it usually just resets that program’s options, and the app often recreates a default. Back it up first in case you want the customised settings back. A legacy Microsoft Backup .set only matters if you still need that old backup job.
References
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