A filename is a label. To change the format, use an app’s export or conversion function and check the new file.
Create a real JPEG copy in five steps
- Keep the original PNG. Show filename extensions using the paths below so you can see the complete name.
- Open this site’s image converter and choose the original PNG, rather than a copy with a guessed extension.
- Select JPEG. Leave maximum width blank to keep dimensions and use 85% as a starting quality setting.
- Convert and download the new .jpg copy. Transparent areas become white in this converter.
- Open the downloaded copy in its intended app and check the image, background and dimensions. If it is rejected, check the destination’s accepted formats and size limit.
This converter supports PNG, JPEG and WebP images. It does not convert PDF or Word files. If an original extension is unknown, ask the sender rather than guessing.
Show filename extensions
Official documentation gives the following English menu paths. Names vary with the interface language and version; we did not operate the Windows or Finder interface in this test.
- Windows 11: File Explorer → View → Show → File name extensions
- macOS: Finder → Settings → Advanced → Show all filename extensions
Renaming and conversion: the measured difference
We copied the diagram PNG, renamed the copy to .jpg, and separately exported the original as JPEG using this site’s converter. The file signatures and SHA-256 checks distinguish a name change from re-encoding.
| Action | File size (bytes) | File contents | Format |
|---|---|---|---|
| Original diagram-source.png | 12,934 | Identical to original | PNG |
| Rename copy to .jpg | 12,934 | Identical to original | PNG |
| Export as JPEG | 13,072 | Re-encoded | JPEG |
Measured on 3 November 2026 · Chromium 151.0.7922.34 · macOS
The renamed copy had exactly the same bytes and PNG signature as the original. JPEG export produced different bytes and a JPEG signature. Some apps identify a file from its contents, so opening successfully does not prove conversion.
Renaming, opening and converting are different
Scroll the table sideways to see every column.
| Action | What changes | What it proves |
|---|---|---|
| Rename photo.png to photo.jpg | The filename | No re-encoding has happened |
| Rename photo.jpeg to photo.jpg | A common JPEG suffix | The existing JPEG contents stay the same |
| Export an image as JPEG | A newly encoded copy | Verify that copy in the intended app |
01The label and the contents
The extension after the final dot helps software identify a file. Renaming an envelope does not rewrite the letter inside. The same distinction applies to photo.png and photo.jpg.
02Check more than the name
Open the exported copy in the intended app. Check that its contents, dimensions and required features are still present. Converting to an image, for example, can remove editable text or other document features.
03If the name was changed accidentally
Restore the original extension if you know it, or check the source of the file. Avoid guessing multiple extensions. A failed conversion and a misleading filename need different fixes.
Sources & further reading
Put it into practice
Image converter
Convert PNG, JPEG and WebP images, adjust quality and resize a copy.
Convert imagesBefore you convert
A short checklist for choosing an image format and checking the result.
Download checklist (.txt)