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To change the extensions of many files at once, use PowerShell to select files with the old extension, preview the proposed names, then run the rename. First make extensions visible so you can confirm which names will change. Renaming an extension changes the filename only; it does not convert the file’s contents.
Show file extensions before you start
File Explorer may hide extensions for familiar file types. Turn them on so a file named report.txt is distinguishable from a name whose extension is not visible.
- Windows 11: In File Explorer, select View > Show > File name extensions. Microsoft’s File Explorer instructions document this path.
- Windows 10: In File Explorer, select View > Options > Change folder and search options. Open the View tab, clear Hide extensions for known file types, then select OK. Microsoft documents this Windows 10 route.
Choose a method for the number of files
| Method | Best suited to | What to know |
|---|---|---|
| File Explorer | A small selection you can inspect and rename individually | Manual renaming is practical for a few files. Do not assume selecting many files and using Explorer’s rename command will replace each extension independently as intended. |
| PowerShell | A larger group with a known source extension | A filename filter targets the intended file type, and -WhatIf lets you preview the proposed changes before they run. |
Batch-change extensions with PowerShell
1. Open PowerShell in the target folder
Open the folder containing the files in File Explorer, then open PowerShell there. Check that you are in the correct folder before running a rename; the command should be scoped to the files you intend to change.
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For example, to rename files ending in .txt to .log, run:
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Get-ChildItem *.txt | Rename-Item -NewName { $_.Name -replace '.txt$','.log' } -WhatIfGet-ChildItem *.txt selects matching files in the current folder. The replacement expression targets .txt at the end of each name, rather than replacing a matching string earlier in the name. The -WhatIf switch displays what would happen without carrying out the rename. This anchored expression is a cautious adaptation of the pattern in Microsoft Learn’s Rename-Item example.
Review the preview and confirm the listed files and destination names are right. If you only want files in this folder, leave the command as shown. Get-ChildItem supports wildcard filtering and a -Recurse option for including child folders; add recursion only if you deliberately want to affect subfolders. See Microsoft Learn’s Get-ChildItem documentation.
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3. Run the rename
After checking the preview, run the same command without -WhatIf:
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Check for name conflicts and remember what a rename does
Before running the command, check that a destination name does not already exist in the folder. Rename-Item does not replace an existing item, so a conflicting destination can prevent a rename. Microsoft documents this behavior in its Rename-Item reference.
Changing photo.webp to photo.jpg changes only the filename. Microsoft Support explains that changing a filename extension does not convert the file to another format or change anything else about it. To make a genuine format conversion, use suitable conversion software or save/export the file in the desired format; do not treat an extension rename as conversion. See Microsoft’s explanation of common file extensions.
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Windows 10 support status
Microsoft Support states that Windows 10 support ended on October 14, 2025. This does not change how the File Explorer or PowerShell steps above work, but standard support for Windows 10 has ended. See Microsoft Support’s Windows 10 notice.
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