File mime type checker

Find out what kind of file you really have

A MIME type (also called a media type or content type) is the standard label that tells browsers and servers what kind of data a file contains, such as image/png, application/pdf, text/csv or video/mp4. Servers send it in the Content-Type header, and upload forms check it to decide what to accept.

Select a file and this checker shows its name, type (MIME type), size and last modified date. It's a fast way to answer "why won't this upload?" or "what is this file without an extension?"

The type is detected by your browser, mostly from the file's extension, so a renamed file may still report the type its new extension suggests.

How to use the file mime type checker

1. Click to choose a file from your device.
2. The tool reads the file details in your browser.
3. Review the name, MIME type, size and last modified date.

Examples

A PDF

Input: invoice.pdf (245,000 bytes)

Output: Type: application/pdf · Size: 245 KB

A Word document

Input: report.docx

Output:

application/vnd.openxmlformats-officedocument.wordprocessingml.document

Office formats have long official types.

A renamed file

Input: photo.png that is really a JPEG

Output: image/png

The type follows the extension, so renaming changes what the tool shows, though the file content stays the same.

Common uses

• Figuring out why an upload form rejects a file.
• Checking the type to set in a server's Content-Type header or an API request.
• Confirming the size of a file before emailing or uploading it.
• Identifying the format of files with unfamiliar extensions.

Tips and things to know

• Common types: image/jpeg, image/png, image/webp, application/pdf, application/zip, text/plain, application/json.
• If an image is too large to upload, shrink it with the image optimizer.
• Photos also carry metadata like camera model and GPS location; see it with the EXIF reader.
• Developers serving files should send the correct MIME type and X-Content-Type-Options: nosniff; check with the HTTP headers lookup.

Edge cases and limitations

• Sizes use 1000-based units rounded to one decimal, so 150,000 bytes shows as 0.2 MB. Your computer may show a slightly different number if it uses 1024-based units.
• File types your browser doesn't know, such as some RAW photos or HEIC on older systems, show an empty type.
• The last modified date is the one stored on your device, which changes when files are copied or downloaded.

Frequently asked questions

What is a MIME type?

It's a two-part label, type/subtype, that identifies a file format, like text/html or image/gif. It was created for email and is now used across the web.

Why does my file show an empty or generic type?

The browser couldn't recognize the extension. Generic binary files often show as application/octet-stream or no type at all.

Is my file uploaded to a server?

The details shown here are read from the file by your browser.

Can I change a file's type by renaming it?

Renaming changes the reported type but not the actual contents. A PNG renamed to .jpg is still PNG data and may not open correctly everywhere.

Related tools

• Exif reader: Upload a image and extract the data out of it.
• Image optimizer: Compress and optimize images for a smaller image size but still high quality.
• Image to Base64: Transform an image input to a Base64 string.
• HTTP headers lookup: Get all the HTTP headers that an URL returns for a typical GET request.
• Text size calculator: Get the size of a text in bytes (B), Kilobytes (KB) or Megabytes (MB).