Firefox Autocomplete Spy displays all autocomplete entries of the browser
Whenever you enter data in Firefox, it is stored in the local database file formhistory.sqlite provided that you have not disabled the saving of form and search data. The file is stored in the root folder of the profile used and since it is not protected, may reveal information about what you have entered in the past to anyone with access to it.
One of the easier options to display all autocomplete information of a Firefox profile is to use the new Windows tool Firefox Autocomplete Spy. It is a free portable program for Windows that runs well on all supported versions of the operating system.
The tool is really simple to use. All you need to do is add a path to a Firefox profile to it and hit the show all button afterwards to display all saved form data.
The program lists the default profile automatically on start which makes things even easier if that is the profile you want to investigate.
Firefox Autocomplete Spy is not limited to local profiles either. If you have access to remote systems and Firefox profiles on them you may load form data from those profiles as well.
It takes less than a second to populate the table with data. Each entry is listed with its field name and value, use count, and the dates it was first and last used.
A search is not provided directly but you may use the report button to generate an HTML report that lists all data in a plain text HTML file which you can search using the browser's search capabilities (hit F3 for a start).
The only other option provided by Firefox Autocomplete Spy deletes all form history of the selected profile.
Note: it is recommended to delete the search and form history directly from within Firefox instead if at all possible as it is the safer option. To do so tap on Ctrl-Shift-Del to bring up the clear history menu in the browser. Select Everything and make sure Form & Search History is selected.
The form history saved by Firefox may reveal information about searches you conducted in the browser and information that you have entered in forms in the past.
Verdict
Firefox Autocomplete Spy is a simple program that displays form and search history of a select Firefox profile when run. While it does so without issues, it may be to simplistic for many tasks. For instance, it is not possible to delete individual entries from the history and since it does not offer search functionality, that too is less ideal than it could be.
All in all though it is still handy for a quick check of historic data, even if it is only to find out if all form data was deleted successfully.
The tool helped me uncover a bug in one of the profiles that I use on a test system. I have configured the browser to delete form & search data on exit, and while I did that, Firefox Autocomplete Spy would display old form data when queried.
Turns out that Firefox does not delete form data if you have unchecked the "remember search and form history" option under privacy in the browser's preferences. I had to enable the option to have Firefox delete the data after which I disabled it again.
Since you cannot display all stored form data in Firefox directly, you need to use third-party tools to do so and Firefox Autocomplete Spy is without doubt one of the easiest to provide you with the means to do just that.