How can I read Chrome Cache files?

Question

A forum I frequent was down today, and upon restoration, I discovered that the last two days of forum posting had been rolled back completely.

Needless to say, I'd like to get back what data I can from the forum loss, and I am hoping I have at least some of it stored in the cache files that Chrome created.

I face two problems -- the cache files have no filetype, and I'm unsure how to read them in an intelligent manner (trying to open them in Chrome itself seems to "redownload" them in a .gz format), and there are a ton of cache files.

Any suggestions on how to read and sort these files? (A simple string search should fit my needs)

Answer 1

I had some luck with this open-source Python project, seemingly inactive: https://github.com/JRBANCEL/Chromagnon

I ran:

python2 Chromagnon/chromagnonCache.py path/to/Chrome/Cache -o browsable_cache/

And I got a locally-browsable extract of all my open tabs cache.

Answer 2

EDIT: The below answer no longer works see here

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Google Chrome cache file format description.

Cache files list, see URLs (copy and paste to your browser address bar):

• chrome://cache/
• chrome://view-http-cache/

Cache folder in Linux: $~/.cache/google-chrome/Default/Cache

Let's determine in file GZIP encoding:

$ head f84358af102b1064_0 | hexdump -C | grep --before-context=100 --after-context=5 "1f 8b 08"

Extract Chrome cache file by one line on PHP (without header, CRC32 and ISIZE block):

$ php -r "echo gzinflate(substr(strchr(file_get_contents('f84358af102b1064_0'), \"\x1f\x8b\x08\"), 10,
-8));"

Answer 3

EDIT: The below answer no longer works see here

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If the file you try to recover has Content-Encoding: gzip in the header section, and you are using linux (or as in my case, you have Cygwin installed) you can do the following:

1. visit chrome://view-http-cache/ and click the page you want to recover
2. copy the last (fourth) section of the page verbatim to a text file (say: a.txt)
3. xxd -r a.txt| gzip -d

Note that other answers suggest passing -p option to xxd - I had troubles with that presumably because the fourth section of the cache is not in the "postscript plain hexdump style" but in a "default style".

It also does not seem necessary to replace double spaces with a single space, as chrome_xxd.py is doing (in case it is necessary you can use sed 's/ / /g' for that).

Answer 4

You can read cached files using Chrome alone.

Chrome has a feature called Show Saved Copy Button:

Show Saved Copy Button Mac, Windows, Linux, Chrome OS, Android

When a page fails to load, if a stale copy of the page exists in the browser cache, a button will be presented to allow the user to load that stale copy. The primary enabling choice puts the button in the most salient position on the error page; the secondary enabling choice puts it secondary to the reload button. #show-saved-copy

First disconnect from the Internet to make sure that browser doesn't overwrite cache entry. Then navigate to chrome://flags/#show-saved-copy and set flag value to Enable: Primary. After you restart browser Show Saved Copy Button will be enabled. Now insert cached file URI into browser's address bar and hit enter. Chrome will display There is no Internet connection page alongside with Show saved copy button:

After you hit the button browser will display cached file.

Answer 5

Try Chrome Cache View from NirSoft (free).

Answer 6

The JPEXS Free Flash Decompiler has Java code to do this at in the source tree for both Chrome and Firefox (no support for Firefox's more recent cache2 though).