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Again, you're mistaken. The Content-Type response header tells the browser what type of file the resource is (mime type). This is _completely different _from the file extension in URL paths.

In fact, on the web all the file extensions are faked through the URL path. For example, this page's URL path is:

https://moz.com/community/q/how-important-is-the-file-extension-in-the-url-for-images

It's not

https://moz.com/community/q/how-important-is-the-file-extension-in-the-url-for-images.html

How does the browser know the the page is an html doc? Because of the Content-Type response header. The faked "extension" in the URL path, is unnecessary.

You can view http response headers for any URL using this tool.

This isn't accurate. File extension (in the url path) is not the same as the **Content-Type **response header. Browsers respect the response header Content-Type over whatever extension I use in the path.

Example: try serving a file /golden-retriever.png with a content type of image/jpeg. Your browser will understand the file as a .jpg. If you attempt to save, your browser will correct to golden-retriever.jpg.

You can route URLs however you want.

Additionally, I'm not aware of any way browsers "leverage cache by content type". Browsers handle cache by the etag/expires header.

I know that descriptive image file names are important for SEO. But how important is it to include .png, .jpg, .gif (or whatever file extension) in the url path? i.e. https://example.com/images/golden-retriever vs. https://example.com/images/golden-retriever.jpg

Furthermore, since you can set the filename in the Content-Disposition response header, is there any need to include the descriptive filename in the URL path?

Since I'm pulling most of our images from a database, it'd be much simpler to not care about simulating a filename, and just reference an image id in my templates.

Example:

1. Browser requests GET /images/123456
2. Server responds with image setting both Content-Disposition, and Link (canonical) headers

Content-Disposition: inline; filename="golden-retriever"
Link: <https: 123456="" example.com="" images="">; rel="canonical"</https:>

@Will Thank you so much for this response. Very helpful.

"If you can't always refer to the image by its keyword-rich filename"...

If I'm already including the canonical link header on the image, and am able to serve from both /images/123456 and /images/golden-retriever (canonical), is there any benefit to referencing the canonical over the other in my image tags?

Thanks for the response. This is what I expected.

I swear I read somewhere that Google may pass some form of value from a child to a parent. i.e. "/famous-dogs/lassie/" could pass some value to "/famous-dogs/", absent any links. Can't find the source, but I suppose I'm a bit worried that I'd permanently lose out on some value if the parent does not exist initially. Considering I may add a "famous dogs" parent page at some point.