Question 1

What does the File Extension Changer do?

Accepted Answer

It batch-changes file extensions: add an extension to files without one, remove existing extensions, or replace one extension with another. You can apply plain or regex find/replace on extensions, convert case, and use common presets like .txt, .csv, .json, .xml, .html. Live before/after preview lets you verify before applying.

Question 2

Can I use regex for find/replace on extensions?

Accepted Answer

Yes. Switch the find mode to 'Regex' and enter a JavaScript-style regex pattern. Useful for patterns like \d+$ to strip trailing digits from extensions, or for converting .jpeg to .jpg.

Question 3

Does it preserve the original filename?

Accepted Answer

Yes — by default the stem (filename without extension) is preserved untouched. Only the extension part is modified, unless you opt into regex find/replace which can match across the whole filename.

Question 4

What happens if two files end up with the same name?

Accepted Answer

Conflict detection flags any rename that would collide with another file in the batch. Collisions are shown as warnings in the preview and excluded from the rename stats.

Question 5

What extra features does this tool have?

Accepted Answer

10 extras: (1) Drag-drop multiple files. (2) Regex find/replace on extension. (3) Case conversion (upper/lower). (4) Common extension presets (.txt/.csv/.json/.xml/.html). (5) Conflict detection. (6) Undo — revert to original names. (7) Stats (changed/skipped counts). (8) Export rename plan as JSON. (9) History (localStorage — last 10 plans). (10) Shareable URL with settings.

Question 6

Are my files uploaded anywhere?

Accepted Answer

No. All rename logic runs in your browser. When you download, the renamed files are packaged locally. Your files never leave your device.

File Extension Changer

How to use