What is the TEMP file format?
A .temp file is a generic temporary file created by an application during processing, installation, or file-saving operations. The extension carries no defined internal format: the actual contents are determined entirely by the program that created the file, and may be binary data, plain text, or any structure the application uses internally during in-progress work.
The .temp extension is a less common, longer alias for the .tmp convention, which dates back to MS-DOS and early Unix. On Windows, most system utilities default to .tmp; .temp is used by some cross-platform applications and certain download managers during active transfers. Both extensions share the same semantics - a scratch or working copy of data that is cleaned up once the parent process completes.
Common scenarios that produce .temp files include:
- in-progress file saves (the app writes to
.temp, then renames to the final name on success) - software installers extracting payload data to disk
- archive utilities decompressing content during extraction
- download managers writing partial data during an active transfer
Because the contents are format-agnostic, identifying a .temp file requires knowing which application created it. A hex editor can inspect the first bytes and cross-reference them against known format magic bytes. .temp files left behind after a crash are generally safe to delete once the creating process is no longer running.
Related placeholder extensions include .bak (backup copies) and .crdownload (Chrome in-progress downloads).
Security & safety
RISK: LOW.temp files themselves are not executable and pose no direct risk. However, malware occasionally uses innocuous-looking temp filenames to hide payloads. If a .temp file appeared without explanation in a sensitive location (Startup, system32) or was delivered via email/download, scan it with an up-to-date antivirus before opening. The "Various programs" link in the old DB pointed to a dead site - no scam risk, just useless.
Format details
in a nutshell- Swish-E temporary index - Swish-E (Simple Web Indexing System for Humans - Enhanced) used .temp files during full-text index builds; project defunct since ~2008.
Programs that open TEMP files
Windows2 apps
Notepad
Open-source Open the .temp file to inspect if it is text-based; reveals the format and any recoverable data. 
HxD (hex editor)
Free Open .temp file to view raw bytes and identify the true format from magic bytes. 
macOS1 app
Linux1 app
file (command-line utility)
Open-source Run 'file yourfile.temp' to identify the true format from magic bytes. Technical details
deep spec| Internal format | No defined structure - internally matches whatever the creating application writes during in-progress work |
| Typical Windows location | `%TEMP%` or `%TMP%` directory (usually `C:\Users\<user>\AppData\Local\Temp`) |
| Typical macOS/Linux location | `/tmp/` or an application-specific cache directory |
| Safety to delete | Safe once the creating process has closed; deleting a file in active use may cause errors in the writing application |
| Identification method | No fixed magic bytes - inspect first bytes with a hex editor and cross-reference known format signatures |
| Relation to .tmp | `.temp` is a longer alias for `.tmp`; semantics, usage, and typical contents are identical |
| Common creation triggers | In-progress file saves, installer payload extraction, archive decompression, partial download writes |
| Encoding | Varies - binary, UTF-8 text, or mixed, depending entirely on the creating application |
| File size range | Bytes to several GB (highly application-dependent) |
| Auto-cleanup | Windows `cleanmgr` can clear `%TEMP%` contents; macOS periodically purges `/tmp` via launchd |
| Related placeholder extensions | `.tmp`, `.bak`, `.part`, `.crdownload` |
| MIME type | `application/octet-stream` (generic binary fallback) |
| Released | 1980s (convention dates back to MS-DOS and early Unix; same era as .tmp) |
TEMP conversions
Community Q&A
asked by usersNo questions yet - be the first to ask about TEMP files.
