This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

Lag when typing

  • 20 replies
  • 38 have this problem
  • 22 views
  • Last reply by cor-el

more options

Im having a s light problem with typing on firefox. when typing, there is sometimes a "lag time" before pressing the key and having the text show up. this only happens in firefox and it happens on all web pages, how do i fix it?

Im having a s light problem with typing on firefox. when typing, there is sometimes a "lag time" before pressing the key and having the text show up. this only happens in firefox and it happens on all web pages, how do i fix it?

All Replies (20)

more options

hello, can you try to replicate this behaviour when you launch firefox in safe mode once? if not, maybe an addon is slowing you down...

Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

more options

I can confirm the behaviour is still present in safemode.

more options

(replies on the forum seem to work again, so for the other contributors reading here, i'll paste the conversation we had via PM:)

philipp Today at 5:02 PM
when you open the windows task manager (ctrl+shift+esc) an go to the processes tab, do you see a high use in cpu-ressources by firefox.exe when this problem happens?

Question2 Today at 5:47 PM
Nope, CPU usage is usually 5-10% and i have 16 gb of ram but only using 2 gb or so when web browsing.

is this 2gb RAM usage just related to the firefox process? this seems to be rather high and cause hangs during "garbage collection" (when firefox is trying to reduce memory usage)... could you try to reset firefox in this case?

more options

No, it's not just the firefox process. Unfortunatley ive got lots of open tabs at the moment, so i cant reset firefox.

Besides, with 16gb of memory im pretty sure firefox can handle it...

more options

firefox for windows is a 32bit application and cannot make use of more than 2gb of ram - if the ram usage comes within the realms of this area, slow-downs and hangs are to be expected...

Firefox uses too much memory or CPU resources - How to fix

more options

It doesn't use 2 gb of ram though.

more options

You can check for problems with the sessionstore.js and sessionstore.bak files in the Firefox profile folder that store session data.

Delete the sessionstore.js file and possible sessionstore-##.js files with a number and sessionstore.bak in the Firefox profile folder.

Deleting sessionstore.js will cause App Tabs and Tab Groups and open and closed (undo) tabs to get lost and you will have to recreate them (make a note or bookmark them).

more options

Well the problem is im trying NOT to delete the session store....

more options

How large is your sessionstore.js file?

Are there any numbered sessionstore-##.js files in the profile folder?

If there are then you should definitely remove those as they have no purpose and force Firefox to scan the directory to find which number to use for the temporary sessionstore file when creating a new file, which happens every 15 seconds (browser.sessionstore.interval).

You can temporarily move the current sessionstore.js file to another location to see if this helps.

more options

I just deleted two extra session store files. The current session store file is 18.7 mb large.

more options

With a sessionstore.js file that large, you may want to consider to increase the browser.sessionstore.interval pref.

more options

What does that setting do exactly?

more options

This pref determines the minimum interval between saving the current browser state to disk in sessionstore.js

  • resource:///defaults/preferences/firefox.js
// minimal interval between two save operations in milliseconds pref("browser.sessionstore.interval", 15000);
more options

How will that help though? Seems like it would only make it easier to lose my session state in the event of a crash.

more options

Yes, that would happen, but it does give Firefox more time to save the session data and complete other tasks.

Do you have any idea why the sessionstore.js file is no large?

Do you have a lot of tabs open with a large session history (back button) or otherwise tend to store data as session data?

more options

Yea i do have a lot of tabs open....

Changed the value to 60,000. Not seeing any change though....

more options

Does this also happen in a New Private Window where Firefox doesn't store data to disk, but keeps it in memory?

You can also try to copy the sessionstore.js file temporarily to another location to test if it is this file that is causing it and not another cause.

more options

What do you mean by new private window?

more options

Firefox 20 version and later have switched to Private Browsing mode per Window.

You can find Private Browsing in the Firefox menu button drop down and in the File menu as "New Private Window".