Extension Case Converter
Change extension case in bulk: all upper, all lower or capitalised
输入文件名（每行一个，仅转换后缀大小写）
About this tool
The extension case converter rewrites just the suffix of each filename:
- Three modes: all upper (.JPG), all lower (.jpg) or capitalised (.Jpg)
- Batch input: convert many lines at once
- Base name untouched: only the extension changes
- Before and after: every row shows the original next to the result
- Copy: take the converted list in one click
When to use it
- Enforce one extension case convention
- Fix case-sensitive breakage on Linux servers
- Batch rename files
- Normalise image and document extensions