Chrome Dev Tools - "Size" vs "Content"

When viewing information about stylesheets in the Network tab of Chrome's dev tools, one column specifies both "size" and "content":

Can anybody shed light on the difference between these two numbers? On some pages the numbers are close and others they are different by a considerable amount.

"Size" is the number of bytes on the wire, and "content" is the actual size of the resource. A number of things can make them different, including:

• Being served from cache (small or 0 "size")
• Response headers, including cookies (larger "size" than "content")
• Redirects or authentication requests
• gzip compression (smaller "size" than "content", usually)

From the docs:

> Size is the combined size of the response headers (usually a few > hundred bytes) plus the response body, as delivered by the server. > Content is the size of the resource's decoded content. If the resource > was loaded from the browser's cache rather than over the network, this > field will contain the text (from cache).

Size is the size of response itself, and Content is the size of resource, that you are accessing.

Compare:

empty cache:

main.js GET 200 OK .. Size: 31.72KB Content: 31.42KB

cached:

main.js GET 304 Not modified .. Size: 146B Content: 31.42KB

In simple terms Google article explain it as Size = Transfer size and Content = Actual size

This is my formula based on reading various articles on this topic (and I am open to improve it further with your comments) Size = Compression(Content) + Response Header

See the image used in this article

Explanation by Google

"Use large request rows" to show both values!

If you don't see the second value (content) you need to click the "Use large request rows" button inside Chrome Network tab:

I found this thanks to the answer on this question here:

https://stackoverflow.com/questions/26445154/chrome-devs-tools-wheres-size-and-content

Size includes response AND request info

Size is a sum of:

1. bytes transferred for the request header
2. bytes transferred for the response header
3. bytes transferred for the response body

From the docs:

> Inspecting the properties of an individual resource, such as its HTTP headers [note the plural, emphasis mine], content, size, and so on.

If you compare the transferSize of a performanceEntry (e.g. for the main document at https://stackoverflow.com/) with the Size in Chrome DevTools' Network tab, you'll see that the two don't match up. That is because the performanceEntry doesn't contain the size of the request header.

Screenshot of the Network tab and a logged performance entry