File Info Viewer

File Info Viewer is a deliberately small tool. You pick a file, and the page lists four things about it: the file name, the size, the MIME type and the last-modified time. It does not open the file, preview it, or read deeper metadata such as photo EXIF data or a document's author. It only shows the four basic properties your browser already knows the moment you select a file. That makes it handy for checking whether an attachment is under an upload limit, confirming a file's format, or verifying when it was last saved.

How to use it

1. Click the dashed box in the middle of the page (it reads 'Click to select any file') and choose a file in your system's file picker. Any file type works.
2. Once you confirm, the box shows your file name and a 'File info' section appears below it.
3. Read the four rows: 'File name', 'File size', 'MIME type' and 'Last modified'. The size row shows both a converted value and the exact byte count.
4. To check another file, click the box again and pick a different one. The new result replaces the old one. Only one file can be checked at a time; multi-select is not supported.

A worked example, computed from the tool's own logic

The size conversion is defined in the code. Anything under 1,024 bytes is shown as B. Below 1,024 × 1,024 bytes it is shown as KB with one decimal place. Above that it is shown as MB with two decimals, and from 1,024³ bytes up as GB with two decimals. Running that logic gives: 1,023 bytes shows as '1023 B'; 1,536 bytes as '1.5 KB'; 2,500,000 bytes as '2.38 MB'; 5,242,880 bytes as '5.00 MB'; and 1,073,741,824 bytes as '1.00 GB'. Note that 1 KB here means 1,024 bytes. If a website defines its limit using 1,000-based units (5 MB = 5,000,000 bytes), the two figures differ by roughly 5 percent, so when checking an upload limit it is safest to compare against the exact byte count shown in brackets.

Limits and known behavior

• No creation date. The file object a web page receives has a last-modified time but no creation time, so this tool cannot show one. That is a limitation of the browser API itself.
• The MIME type is decided entirely by your browser, usually from the file extension. For unfamiliar formats or files with no extension, the row reads '(browser could not detect a MIME type)'. That does not mean the file is damaged.
• Because the MIME type is inferred from the extension rather than from the file contents, renaming an .exe to .jpg will likely still report an image type. Do not use it to judge whether a file is safe or what it really is.
• Only four properties are shown. Image dimensions, video duration, document author, EXIF data and similar internal metadata are not read.
• One file at a time. Folders are not supported, and there is no drag-and-drop; you click to choose.
• The last-modified time is formatted for your interface language (en-US formatting in English, zh-CN in Chinese) and uses your device's local time zone. Copying, downloading or extracting a file can change this time, so it may not be when the content was originally written.

Why can't I see the file's creation date?

A web page only receives a file's name, size, type and last-modified time. Operating systems record and carry over creation time in different ways, and the browser standard does not expose that field. If you need it, open the file's properties window in your operating system.

Why does the size differ slightly from what my system shows?

There are two usual reasons. First, the unit base: this tool divides by 1,024, while some systems and cloud drives divide by 1,000. Second, rounding: KB is shown with one decimal and MB with two. The byte count in brackets is exact, so compare that when precision matters. Also, 'size on disk' in your operating system is the space allocated on the drive, which is usually a little larger than the file's actual size and is a different concept.

What if the MIME type says it could not be detected?

It means the browser has no registered type for that extension. This is common with niche professional formats, extensionless files, or custom extensions. The file itself is normally fine, and the other rows remain valid. If you need to confirm the real format, open the file in the appropriate application rather than relying on this row.

Can I use it to tell whether a file was modified?

Not reliably. The last-modified time can be rewritten by any program or set by hand, can change during copying or transfer, and this tool does not compute a checksum. Treat it as a rough hint, for example to check you picked the most recently saved version.

How large a file can it handle?

The tool only reads the file's metadata and never loads the contents into memory, so even very large files show results immediately. The unit conversion in the code goes up to GB.

Privacy and processing

Everything runs in your browser, and the page code contains no network requests. After you pick a file, only its name, size, type and last-modified time are read. The contents are never read and nothing is uploaded to a server. When you close or refresh the page, the result is gone.