About Ext Decoder
A small, focused tool for a genuinely common question.
Why this exists
Typing a filename into a search engine to figure out what it is — or whether it's safe to open — is a common need. Most existing answers either want you to upload the file somewhere first or bury a real answer under ads and unrelated content. Ext Decoder answers the single question "what does this extension mean?" from the filename alone, instantly, with no upload and no account.
Who built it
Ext Decoder is built and maintained by Gouse Labs, the personal brand of Gouse Shaikh, a backend software engineer who builds small, practical tools he wants to use himself. Source and other projects are on GitHub.
Other tools from Gouse Labs
How it works
The entire extension dataset — over 150 formats, plus known ambiguous extensions, dotfiles, and extensionless filenames — ships as static data bundled with the page. Parsing and lookup both run synchronously in your browser with plain TypeScript; nothing is ever sent to a server. See the FAQ for details on how specific edge cases (compound extensions, hidden files, unknown extensions) are handled.
What it isn't
Ext Decoder identifies file formats from filenames. It never inspects real file bytes or content (by design — there's no upload), so it cannot and does not make any claim about a specific file's actual, true safety. See our Privacy Policy and Terms & Conditions for the full details.