Batch Change File Extensions Online

Change file extensions in bulk directly in your browser. Convert .txt to .md, standardize casing from .PNG to .png, add missing extensions, and more — all privately and instantly.

How It Works

FileTango's Batch Extension Changer reads file names locally in your browser and applies your chosen extension transformation. You can replace all extensions with a new one (e.g., change every .txt to .md), standardize casing (convert .PNG and .Png to .png), or add an extension to files that lack one. The tool generates an instant preview showing each file's current and proposed name, and highlights any issues. When you are ready, download a ZIP archive with the updated files. Because everything runs client-side, there is zero upload time and your files remain completely private.

Step-by-Step Tutorial

Select files to update

Click "Select Files" and choose the files whose extensions you want to change. Multi-select is supported — hold Ctrl (Windows) or Cmd (Mac) to pick multiple files.
Set the new extension

Enter the desired new extension in the text field (e.g., "md", "jpg", "png"). You can also choose to standardize casing to lowercase or UPPERCASE without changing the extension itself.
Preview the changes

Click "Preview Changes" to see a table of every file with its current name and proposed new name. Review the list carefully — the tool highlights any issues such as files that would have the same name after the change.
Download the result

Click "Download ZIP" to receive a ZIP archive containing your files with updated extensions. Optionally, export the change plan as a CSV for documentation.

Common Use Cases

Convert plain text files (.txt) to Markdown (.md) for use in documentation tools
Fix incorrect extensions — for example, rename .jpeg files to .jpg for web compatibility
Standardize extension casing across assets (.PNG, .Png → .png) for consistent builds
Add extensions to files that are missing them, such as downloaded data files
Prepare files for a specific platform that requires a particular extension format
Batch convert screenshot extensions before sharing or uploading to a CMS

Tips & Best Practices

Don't include the dot when entering a new extension — just type 'md' instead of '.md'.

Use the lowercase casing option to normalize extensions across a mixed set of files (e.g., .JPG, .Jpg, .jpg all become .jpg).

Remember that changing an extension does not convert the file format — make sure the content matches the extension you choose.

Process different file type groups separately if you need different target extensions for each group.

Use the preview table to catch any unexpected results before downloading the ZIP.

Frequently Asked Questions

Does changing a file extension change the file format?

No. Changing the extension only changes the name label, not the file's internal format. For example, renaming a .png to .jpg does not re-encode the image. Use this tool when the file content already matches the desired format but the extension is incorrect or inconsistent.

Will my original files be modified?

No. FileTango creates new copies of your files with updated extensions and packages them in a ZIP archive. Your original files on disk remain completely untouched.

Can I change extensions for specific file types only?

Currently the tool applies the extension change to all selected files. To target specific types, select only those files when using the file picker, or process different groups in separate batches.

What is the difference between changing an extension and converting a file?

Changing an extension updates the filename suffix without altering file contents. Converting a file transforms the actual data — for example, re-encoding a PNG image as a JPEG. FileTango handles extension changes; for format conversion, you need a dedicated converter.

Can I remove an extension entirely?

Yes. Leave the new extension field empty and FileTango will strip the existing extension from all selected files, giving you extensionless filenames.

Is there a limit on file sizes?

There is no server-side limit since everything runs in your browser. The practical limit depends on your device's available memory. For very large files (several GB each), process them in smaller batches.

Privacy & Security

All file processing happens entirely in your browser using the Web File API. Your files are never uploaded to any server, never stored in any database, and never transmitted over the internet. We physically cannot see or access your files.

When you click Download, a ZIP archive is assembled locally in your browser's memory and saved directly to your computer's default download folder. The entire pipeline — from file selection to ZIP creation — runs on your device.

FileTango does not require an account, does not collect personal information, and does not track which files you process. Your privacy is guaranteed by architecture, not just by policy.