Firebug shows some requests in Gray

Question

Firebug shows some requests in Gray(screenshot attached and marked in Red) with status code 200 and some requests shows black with status code 200. What is the difference between two requests?

firebug output

I would assume gray entities are entities that have been loaded from the cache somehow. Let me investigate. — Mathias Lykkegaard Lorenzen, Feb 15 '12 at 09:59
Yes,Thats what my assumption before google it. But after googling most of document says if any file loaded from cache then the status would be 304. But here it shows 200. — Selvakumar Ponnusamy, Feb 15 '12 at 10:04

score 6 · Accepted Answer · edited Jun 20 '20 at 09:12

6

The gray requests are the ones loaded from the cache, as described in a feature-promo here:

http://getfirebug.com/network

Cached or not cached

Not all network requests are equal - some of them are loaded from the browser cache instead of the network. Firebug provides status codes for every request so you can quickly scan and see how effectively your site is using the cache to optimize page load times.

Edit As for your concern regarding 200-codes and 304 codes, they also display this image on their website next to the above quote.

enter image description here

In other words, it would seem as if 200 still means that it is loaded from the cache. I do agree that it's a bit strange. I'm trying to uncover more details.

Edit 2 I would assume that the server sends out 200-codes, but the browser chooses to ignore them and run the cached content anyway (perhaps by assuming it didn't change, or perhaps because the new page loaded is in the same directory as the old one?).

edited Jun 20 '20 at 09:12

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answered Feb 15 '12 at 10:00

Mathias Lykkegaard Lorenzen

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Yes,Thats what my assumption before google it. But after googling most of document says if any file loaded from cache then the status would be 304. But here it shows 200. – Selvakumar Ponnusamy Feb 15 '12 at 10:05
The new page is in another directory only. But the JS files which are gray and black been used in both the pages. – Selvakumar Ponnusamy Feb 15 '12 at 11:14
My above theories is all I can give to you. – Mathias Lykkegaard Lorenzen Feb 15 '12 at 11:49

score 1 · Answer 2 · answered Nov 08 '12 at 16:27

I'm citing Jan Honza Odvarko, firebug lead developer, from the actual firebug google group:

1) Requests displayed in Gray (with status code == 304) represents cases where the response is coming from the browser cache.

2) Requests displayed in black (with status code == 200) represents cases where the response is coming from the server (not cached)

3) Requests displayed in gray with special background (whatever status code) come from BFCache, see: http://www.softwareishard.com/blog/firebug/firebug-tip-what-the-heck-is-bfcache/ (the background has been introduced in Firebug 1.10)

Firebug shows some requests in Gray

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