Restore File Extension

When you need to restore a file extension

A file extension is the few characters after the dot in a file name (.pdf, .jpg, .docx). The operating system and applications use it to decide which program should open the file. When the extension is lost, changed by hand, or doesn't match the actual content, the file stops opening the usual way even though the data inside is intact.

The extension restore tool detects a file's real format by its content, not by its name, and returns the same file with the correct extension. The file bytes are not changed - only the extension in the name changes so the file opens with the right program again.

How it works

A file's format is defined by its internal structure, not by its name. Most formats start with a characteristic signature: PNG has its own, PDF has its own, ZIP, DOCX, and JPEG each have theirs. The tool reads the file content, matches it against known formats, and reports the real type even when the name is misleading.

Once the format is detected, you get the original file unchanged, but with the correct extension. For example, if a PNG image was mistakenly saved as photo.jpg, the tool recognizes PNG and returns photo.png. The content stays the same - only the extension changes.

When this helps

Restoring an extension is useful when:

• the extension was accidentally deleted or changed during renaming;
• the file was exported from a system or archive without an extension;
• a downloaded file has an unclear name and won't open;
• the extension doesn't match the content (for example, a document saved with an image extension);
• you need to know what a file is before opening it.

This is common with old archives, database exports, email attachments, and files that passed through several systems that may have lost or rewritten the name.

How restoring an extension differs from conversion

It's important not to confuse restoring an extension with conversion. Conversion changes the data format itself: for example, it turns a PNG into a PDF by rebuilding the content. Restoring an extension rebuilds nothing - it only detects the real format and brings the file name into line with it.

If a file is actually a PNG image but named .jpg, restoring gives it the honest name .png. It does not turn it into a real JPEG - that requires conversion. So restoring is the right choice when the data is correct and the only problem is a wrong or missing extension.

Security and privacy

The file is processed only to detect its format. The content is not published or shared with third parties, and the file itself is deleted automatically after processing. Format detection requires no software installation and works right in the browser through file upload.

If the content cannot be matched to any known format, the tool says so honestly and does not assign a random extension. That way you never get a false name that only adds confusion.

What to do after the format is detected

Once the correct extension is restored, the file opens again with a double click in the right program. From there you can work with it as usual: open it, edit it, or, if you need a different format, run a conversion.

If after restoring the extension you actually need a different format - for example, a PDF from an image or an assembled document - use the matching converter. Restoring an extension is the first step: first understand what the file is, then decide what to do with it.