Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I filled out a lengthy form on a webpage which rejected my submission due to a server error. I can't seem to recover the form input.

Is there any way in Firefox to look into caches, history, etc. to recover this information?

share|improve this question
up vote 5 down vote accepted

I'd recommend you to install Lazarus - it has saved my butt enough number of times.

share|improve this answer
+1, thanks for the suggestion! – Jason S Sep 26 '10 at 13:48
Lazarus is promising. But, alas, Lazarus is dead (!). Lazarus does not work. The contact form on the site is broken. And the developer does not respond. – Nicolas Barbulesco Apr 15 '14 at 11:39
Also lazarus somehow conflicts with firebug. – Tomáš Zato Sep 13 '15 at 0:06

Whew! I figured out a solution -- I was able to hit the "back" and "forward" button with the "Live HTTP Headers" extension capturing incoming/outgoing traffic, and the form information was part of a POST response. (Firefox will resend form input, not sure where that's stored, but doesn't have any obvious built-in way to display it to users)

share|improve this answer
I think it's stored in RAM, since you can hit "Back" to get back to the form with your data filled in, but I've never heard of Firefox restoring those form values after you close and restart the browser. – David Z Sep 1 '10 at 18:47
You might want to have Lazarus [ ] installed, if something like this happens again. – Sathya Sep 1 '10 at 21:15
@Sathya: consider posting as a separate answer, I'd vote it up. – Jason S Sep 25 '10 at 16:31
I've posted the comment as an answer. – Sathya Sep 25 '10 at 16:49
Maybe this wasn't true three years ago, but Firefox's built-in web developer tools currently have facilities which let you extract the information in a similar way. Just answered here. – sh1 Dec 7 '13 at 9:08

Another possible solution to recover your data is to make a core dump of Firefox (assuming you are using it under Linux or similar). See this answer for more details:

share|improve this answer

I'm afraid form contents aren't cached... Regular input fields (single line) may be saved with auto fill, yet text area's (multiple lines, the one that you probably typed in) aren't.

share|improve this answer

The Web browser definitely has the form data in memory. The difficulty is : How to retrieve this data ?

Here is my idea. I have not tried it. On paper, it works. This answer applies to Firefox and to other Web browsers.

In short : Reload the page, while examining the headers.

  1. Set up the machinery. We need a machinery to examine the HTTP traffic sent from the Web browser.
    • The best choice is the extension LiveHTTPHeaders for Firefox. But I think that installing this extension needs a restart of Firefox. Don't restart Firefox, of course ! It would be nice to be able to install this machinery without restarting Firefox. Otherwise, you just need to have this extension installed beforehand. If need arises, simply use a time machine. ;-)
    • If you cannot have the machinery ready in the Web browser, there is another option. This option is heavier. But its mighty strength is that it works for all Web browsers, and without restarting them. Install a simple Web server, or set up a proxy server (like Squid), on your machine. Make sure that your server logs the inbound traffic, with the full headers. And place a rule in the OS for redirecting all outbound requests towards This can be done with a hosts file.
  2. Test the machinery. Create a new window in your Web browser. Write some text in Wikipedia here, and click Preview. Then verify that in your machinery you see your written text. If your machinery is the server option, you have to toggle off the redirection rule to load the Wikipedia form, and to toggle it on afterwards.
  3. To reload the page, right-click where the form was, and choose Reload. This is important. In some webmails, this will reload only the frame where the form was. Here we want to reload only as little as possible. If you click the button Reload in the address bar or in the button bar, or if you press Apple R, you risk reloading the whole page, and in some webmails this is shooting yourself in the foot.
  4. Normally, the Web browser will ask you : Do you want to send again the form data ? If you get this question, this is a good sign. Choose Send again.
  5. Examine the POST data sent, with the machinery set up in the step 1. Here you shall find your wanted data.
  6. Come tell us here that this solution has worked !
share|improve this answer

I found a new addon that can be used to recover lost postdata: Form History Control

The author claims:

This plugin also stores text from editor fields as you type, so you never have to loose your work when disaster strikes. Recover your lost work after session timeouts, network failures, browser crashes, power failures and all other things that will destroy the hard work you just put into writing that important email, essay or blog post.

EDIT: Oh, it indeed saved this post. :)

share|improve this answer
This extension is a (very) nice idea. But it is too complicated. This extension proudly says that it "auto-saved text entered in any form". Does it save "contenteditable" user-entered data ? For instance, Disqus comments and Wikipedia WYSIWYG edits. – Nicolas Barbulesco Aug 19 '14 at 9:19
@NicolasBarbulesco I don't know, try it, then tell the developer if it doesn't work. I suppose it works for input and textarea fields only, and form postdata. The primary reason I downloaded it because many stupid forums simply log you out if you are writing a post for too long, eating your whole writing... – Calmarius Aug 19 '14 at 10:47

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .