Check the source format
Know the file’s real format before changing its displayed extension.
Extension rename tool
Change File Extension Online
Change a filename extension locally in your browser. Use the preview to review every new filename before exporting a renamed ZIP.
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Before you export
Know when an extension change is the right fix
An extension rename is appropriate when the file already has the correct internal format but its visible suffix is missing, inconsistent, or written with unexpected capitalization. Common cleanup jobs include normalizing .JPG to .jpg, restoring .pdf after an import removed the suffix, or applying the same extension style across assets prepared for a case-sensitive server.
It is not a substitute for conversion. A word-processing document renamed from .docx to .pdf is still a DOCX file, and an image renamed from .png to .jpg still contains PNG data. If an application cannot open the result, restore the original extension and use software that converts the underlying format. Keep an untouched source copy whenever the real format is uncertain.
Guide
Change names carefully when extensions are involved
A filename extension tells an operating system which app might open the file, but renaming it does not convert the underlying data. Use this tool for naming cleanup only. For a true format conversion, use a dedicated converter.
Use one consistent case
Normalize extensions such as .JPG and .jpg for cleaner collections.
Do not treat renaming as conversion
Changing .txt to .csv does not turn text data into a spreadsheet file.
Frequently asked questions
Does changing an extension convert a file?
No. It only changes the filename extension, not the file’s contents or format.
Can I change extensions for several files?
Yes. Select files, add an extension rule, review the names, and export.
Are files uploaded during extension changes?
No. The rename process runs locally in your browser.