Regarding the other tabs not loading...

I think the reason might be that Firefox only opens a certain number of connections per server at a time. I'm not sure of the consequences of changing those settings (the articles I've read are not clear that it helps with slow sites).

Firefox's developer tools have a Network panel you can use to see which components of a page are loading slowly. This might provide some insight on what Firefox is waiting for.

In a tab, before loading the first page from the site, open Firefox's Web Console by pressing Ctrl+Shift+k. On the black toolbar, click Network. Then load the page and all the resources requested should appear in chronological order. There are timing bars and other information available if you click any of the rows.

If you want to share a URL to volunteers to try out, you could do that, too.

I know about the Firefox network panel, I am a developer myself. It won't help to see whats causing it to be slow, as when generating feeds or running large scripts then I am expecting the page to take a long time to load, but I also expect other pages to work too. I know exactly what is running slowly, its the page itself as its waiting for a php script to run before sending anything back to the browser, but Firefox will just stop any other tabs from loading anything on the same domain. not after a certain amount of connections but all together.

I can start Firefox from scratch with a single tab open and if that tab hasn't loaded then I can't open any other tabs to that domain, so unless Firefox's connection limit is one then i don't think that's the problem, unless it's not closing connections when i quit Firefox.

And if the server does not come back with anything then Firefox will never recover, it wont time out it will just keep running and I will have to restart the browser for any sites form that domain to work again, it's a serious issue as being a developer, I expect pages to take a long time to load very often and its ridiculous that it stops loading other pages if one is waiting.

Funnily enough chrome has very similar behavior, but not as bad, however I would prefer to continue using Firefox rather than chrome.

P.S. - Thanks for replying

What result do you get if you Ctrl+click each of these quickly in the following order:

• http://www.jeffersonscher.com/res/slowpage.php - has sleep(30)

• http://www.jeffersonscher.com/res/flushandsleep.php - has sleep(15)

• http://www.jeffersonscher.com/res/jstest.php - no delay

Expected result: third tab loads promptly, second tab after about 15 seconds, first tab after about 30 seconds. Or in other words, I do not expect the second and third tabs to wait on the first one.

I suggest that if you have turned on "When I open a link in a new tab, switch to it immediately" in the Options (on the Tabs panel), you turn it off so you can Ctrl+click the links as quickly as possible.

That seems to load them fine, bit odd, the sites its happening on are accessed via a hosts file change, so manual dns, dont think that would make a difference though, sometimes its fine, others its really bad.

I have got the same problem, it is still there. The above example seems to work, but it is three different URLs.

The problem appears when I open this same URL in more tabs: http://www.jeffersonscher.com/res/slowpage.php

Then, 30s to finish first, 30s to finish second tab...so if four tabs are opened the same time, it takes TWO MINUTES to load all of them.

You might say why open same URL in more tabs, but I am experiencing this with some sites. I am not sure how Firefox decides whether it is the same or different URL. But I am definitely having this problem in our supplier's extranet which is quite slow due to long queries waiting for the server. I cannot give you passwords, but basically this problem comes when I open these URLs in more tabs: https://www.media4web.cz/reg/tickety-spravce.php https://www.media4web.cz/reg/index.php https://www.media4web.cz/reg/info-whois.php?postDomains=xxx.com (this is just for URL info, you cannot enter without having login+psw)

Firefox 32.0.3, XP 32bit CZ SP3, reproduced on two PCs one single core, second dual core. Same problem on Win Vista 32bit CZ, where I tried Firefox 3.6.28, 12.0, 32.0.3 ...all having the same problem.

Moreover, another problem that comes with this is CPU load. It is very much visible on XP single core PC which is quite weak config these days (Athlon 64bit 3000+, 2GB RAM...but 32bit XP). When Firefox started and only four tabs opened one by one as fast as possible with the above URL (http://www.jeffersonscher.com/res/slowpage.php), nothing else .... then it is burning CPU to 100% for two minutes. The same happens on other machines, but more tabs has to be openned as these CPUs are more powerful. How can a site that is basically doing nothing than waiting for the response from remote server eat so much CPU? As I was testing more versions of Firefox, I am positive that older version 3.6.28 was not having the problem with the CPU drain (1-2% CPU load compared to 45-60% load on the very same hw and system under Firefox 32.0.3).

This must be a bug, maybe two. Could you please reproduce it on other systems? Regarding the CPU problem, with as weak configuration as possible or more tabs opened?

Hi raduz, I had not tested that before. To explore further, I tried this:

• right-click the URL > Copy Link Location

• Open the Web Console (Ctrl+Shift+k) and click Network, then paste the URL in the address bar and press Enter: It shows the request is sent and Firefox is waiting the 30 seconds.

• Open another tab, open the Web Console and click Network, then paste the URL in the address bar and press Enter: It does not show the request until the first tab finished loading at which time Firefox sends the request and starts waiting the 30 seconds.

It's not conclusive evidence, but it suggests that if Firefox has an open request for a URL, it does not re-request the URL for a new tab until the first request has completed.

As a workaround, you can modify the URL with a query parameter, although this isn't safe with every website. If you Ctrl+click each of these links you should find they load simultaneously instead of serially:

http://www.jeffersonscher.com/res/slowpage.php http://www.jeffersonscher.com/res/slowpage.php?asdf http://www.jeffersonscher.com/res/slowpage.php?1234

It's not practical to hack URLs by hand, but you might be able to use an add-on or find/create a Greasemonkey userscript to modify links in a page, if they are links, or create a bookmarklet that adds a random parameter by using the current time.

Regarding CPU utilization, could I suggest starting a separate thread for that? There's a link at the top of the page for "Ask a Question". As you click through the form, scroll down past suggestions if they are not relevant to the question.