<p>Is there a good way to see what format an image is, without having to read the entire file into memory? </p>

<p>Obviously this would vary from format to format (I'm particularly interested in TIFF files) but what sort of procedure would be useful to determine what kind of image format a file is without having to read through the entire file?</p>

<p><strong>BONUS</strong>: What if the image is a Base64-encoded string? Any reliable way to infer it before decoding it?</p>

Most image file formats have unique bytes at the start. The unix
```
file
```
command looks at the start of the file to see what type of data it contains. See the Wikipedia article on
Magic numbers in files
and
magicdb.org
.