About this tool
Review filename extensions without reading file contents. The tool distinguishes simple extensions, compound extensions, and names with no extension.
How to use
- Paste one filename per line or select multiple local files.
- Choose whether to recognize common compound extensions.
- Review filenames, base names, and extensions, then copy or download the list you want to keep.
Features
- Accepts pasted filenames or selected files.
- Distinguishes the final extension .gz from the compound extension .tar.gz in archive.tar.gz.
- Treats names such as .gitignore, .env, and README as having no ordinary extension.
Extension rules
- Recognizes common compound extensions such as .tar.gz, .tar.bz2, .tar.xz, .user.js, .min.js, .min.css, and .d.ts by default. Other names use the part after the last dot as the extension.
- Hidden files with only a leading dot, such as .gitignore and .env, have no extension by default. The final extension of .env.local is .local.
- An extension comes from the filename and does not prove the file's actual format. Use the File Type Detector to check the contents.
Limits
- Enter one filename per line. You can select up to 1,000 files at a time.
- This tool only extracts filename information. It does not rename files or convert their contents.
Privacy
All files are processed only in your browser and are never uploaded to a server.
File names, entered text, and results are processed only in your current browser. Your input is not saved automatically. Download any results you want to keep before clearing the tool or leaving the page.
FAQ
What is the extension of archive.tar.gz?
Its final extension is .gz. With common compound extension recognition enabled, the combined result is .tar.gz.
Is .gitignore an extension?
This tool treats .gitignore as a hidden filename with no extension by default. It recognizes .local as the extension of .env.local.
What happens to files with no extension?
Names such as README and Makefile are labeled as having no extension. They are not treated as errors.
Does changing the extension convert the file format?
No. Renaming a file does not convert its bytes. Check the contents or use an appropriate conversion tool to change the format.