Changing a filename extension changes how Windows and apps interpret the file; it does not convert the underlying format. Only change an extension when you know the file already contains the corresponding format or a workflow explicitly requires it.
Steps
- In File Explorer, enable View > File name extensions on Windows 10.
- Select the file and choose Rename.
- Change only the characters after the final period, then press Enter.
- Accept Windows’ warning only if you understand the consequence.
- Open the file with the appropriate app and, if it fails, rename it back to the original extension.
How it works
A JPG renamed to PNG is still JPEG data. Real conversion requires opening/exporting or using a conversion tool that rewrites the file contents.
Important considerations
Windows 10 is unsupported. Keep a backup before batch-renaming extensions, and be cautious with double extensions such as `document.pdf.exe`.
Practical guidance
Batch extension changes can break many files at once, so test one copy first. If extensions are hidden, a rename may accidentally produce names like `report.pdf.txt`; enabling extensions prevents this confusion. For scripts and executables, extension changes can also alter security prompts and application associations.
Additional details
When a file was downloaded without an extension or with the wrong one, inspect its source/application and, when possible, use the creating program’s Open/Export feature. Advanced users can inspect file signatures with trusted tools. Guessing extensions until something opens can produce misleading results or expose unsafe content.
Kermit Matthews is a freelance writer based in Philadelphia, Pennsylvania with more than a decade of experience writing technology guides. He has a Bachelor’s and Master’s degree in Computer Science and has spent much of his professional career in IT management.
He specializes in writing content about iPhones, Android devices, Microsoft Office, and many other popular applications and devices.