The tool identifies the true file format by its internal structure, not its extension. You get the precise MIME type, such as `application/pdf`, even if the file is named `photo.jpg`. It also displays technical details like size, checksums, and, if the format is supported, textual content or an image preview for visual confirmation.
When this is useful
A colleague emailed an attachment named `report` without an extension, and you don't know which program to use. Uploading it instantly reveals it's an Excel spreadsheet, so you can work with it right away. In another case, you downloaded `image.png` from a website, but it won't open in a viewer. The tool analyzes the signature and reports that it's actually a PDF document, explaining the error.
Step-by-step instructions
- On the tool's page, click the selection button and choose the problematic file from your device.
- Wait for the upload and automatic analysis to complete, which usually takes a few seconds.
- Review the result: the most likely file type and its MIME type are shown at the top.
- Below, you can see extra information like the exact byte size and SHA-256 hash sums.
- If the format is recognized as text or an image, scroll down to view the content.
How to verify the result
If the result shows a generic type like `application/octet-stream`, it means a precise signature wasn't found, and the file might be in a proprietary or corrupted format. Compare the visual preview with the expected content: if a text file displays as unreadable characters, it's likely binary data. If an upload error occurs, ensure the file is not empty and does not exceed the 20 MiB limit for free usage.
Important limitations
The tool does not rename the file or alter its content; it only provides an analysis report. Type identification is based on signatures and is not a 100% guarantee, as malicious actors can intentionally spoof headers. This check is unrelated to security: a file might be identified as a harmless PNG but still contain a malicious payload that exploits vulnerabilities in a viewer.