What is the CACHE file format?
The .cache extension is used for cache memory files, which are utilized by many programs - for example, web browsers, image editors, and game engines. .cache files store various types of data recently accessed by a given application.
Cached data can be quickly retrieved when needed, which speeds up many application processes: the program does not need to recalculate or re-download information every time the user makes a related request. Common examples include decoded images, downloaded web resources, computed thumbnails, and precompiled shader data.
.cache files can grow large in size, but it depends on the application and the type of stored data. While many caches are binary files, some applications write plain-text, .json, or .xml caches, and others use a small embedded .db (SQLite) database. The file layout is entirely application-specific - there is no universal .cache format. On Windows, cache folders typically sit under %LOCALAPPDATA%\<App>\Cache; on macOS under ~/Library/Caches/<App>; on Linux under ~/.cache/<App>.
A .cache file can be safely deleted if available disk space is an issue - the program will rebuild it on next use. Many apps also offer a dedicated clear-cache option in their settings.
.cache files are created and written by the application in the background, so users rarely encounter them directly. They hold no original content and carry no value outside the application that produced them.
Security & safety
RISK: LOWA .cache is passive data, not executable, so the file itself is not a malware vector. Two mild cautions: caches can hold remnants of private data (cached pages, thumbnails of images you viewed), so they're worth clearing for privacy; and deleting a cache an app is actively using can cause a momentary rebuild or, rarely, glitches until it regenerates - so prefer the app's own 'clear cache' option and close the program first. Otherwise, removing a stale .cache to reclaim space is generally safe.
Format details
in a nutshell- Web browser cache (Firefox/SeaMonkey, Chromium) - Browsers store cached web resources in app-private cache files/folders; clear via the browser's 'clear cache', not by opening the files.
- .NET assembly / GAC cache - The .NET runtime keeps compiled/assembly cache data; managed by the framework, not user-editable.
- Game/app asset cache (e.g. Source-engine, Photoshop Album) - Games and media apps write .cache files of preprocessed assets/thumbnails that regenerate if deleted.
Programs that open CACHE files
Windows3 apps
Mozilla Firefox
Open-source For a browser cache: clear it via Settings > Privacy & Security > Cookies and Site Data > Clear Data (don't hand-edit the cache files). 
The application that created it
Built-in Don't open the .cache directly - manage it through the owning app (e.g. browser Settings > Clear browsing data) or just let the program use it.
Notepad++ / a hex editor (HxD)
Open-source Open the first bytes only to identify an unknown .cache (text/JSON vs binary). Don't edit a binary cache by hand. 
macOS1 app
The application that created it
Built-in Manage via the app (or clear ~/Library/Caches/<app> when the app is closed). Use a hex/text editor (Hex Fiend) only to identify the type. 
Linux1 app
The application that created it
Built-in Let the owning program manage it, or clear ~/.cache/<app>. Use 'file'/a hex editor to identify an unknown one. Technical details
deep spec| MIME type | application/octet-stream (default); text/plain for text-based caches |
| File signature (magic bytes) | No universal file signature - byte layout is defined entirely by the producing application |
| Encoding | Binary or plain text (JSON, XML) - application-dependent |
| Typical file size | A few KB to several GB; browser, game, and media caches grow largest over time |
| Internal structure | Application-private layout of cached fetched or computed data plus lookup keys for fast retrieval |
| Container format variants | Flat binary blob, plain-text key-value pairs, JSON, XML, or embedded SQLite database |
| Compression | Application-dependent; some caches store compressed blobs (e.g. zlib-deflated HTTP responses); many text and JSON caches are uncompressed |
| Checksum / integrity | Application-dependent; some caches store per-entry hashes or HTTP ETags to validate freshness |
| Encryption / obfuscation | Typically absent; some messaging apps and DRM-aware players encrypt or obfuscate their cache |
| Windows storage location | %LOCALAPPDATA%\<App>\Cache or %APPDATA%\<App> |
| macOS storage location | ~/Library/Caches/<App> |
| Linux storage location | ~/.cache/<App> per XDG Base Directory Specification |
| Associated operating systems | Windows, macOS, Linux - the .cache extension convention is cross-platform |
| Safe to delete | Yes - the application rebuilds the cache on next use; clear via app settings when stale or oversized |
| Cache invalidation | Program-controlled: entries expire by timestamp, file hash, or ETag match; no standard mechanism across formats |
| Released | N/A (the 'cache' convention is generic and long-standing across operating systems) |
| Latest version | N/A (no specification - defined per application) |
CACHE conversions
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