I have an shortcut on several Windows PCs that points to Chrome with --proxy-pac-url.

Full Target: field in shortcut properties looks like this:

"C:\Program Files (x86)\Google\Chrome\Application\chrome.exe" --proxy-pac-url=file://C:/Local/Drive/Path/To/proxy.pac

One PC is always on and didn't restart Chrome in a long time. It still runs Chrome 71. On this PC .pac still works and I can access dynamically proxified resources. On the rest, where Chrome was updated to 72 and restarted it no longer works - Chrome tries to access resource directly and fails. Additionally, I can't debug it, since chrome://net-internals/#proxy shows is empty of any info save for re-apply/clear buttons.

So, what broke, how can I debug this and how to make a specific instance of Chrome run with specific .pac once again? Without always swapping options by hand, of course.

5 Answers 5


Chrome 72-75:

  • As suggested in this bug report, you can disable 'Enable Network Service' in chrome://flags to go back to the old behaviour that supports file:// pac files. Starting Chrome from the command-line with --disable-features=NetworkService has the same effect.

Chrome 76:

  • It seems that the 'Network Service' option has been removed from chrome://flags (see the code commit).

    You can still run Chrome with --disable-features=NetworkService (ref) (e.g. /Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --disable-features=NetworkService on a Mac), and it seems to read the PAC file ok, though there might be some issues (because lots of related code seems to have been deleted already - see this issue - I guess YMMV, and this won't be a long-term solution.

    As suggested in the bug report, you are probably better either installing a browser plugin that lets you define PAC settings, or use an http(s) PAC file.

  • 2
    Note that even --disable-features=NetworkService is only a temporary fix; from the linked bug, "we will not be supporting file:// URLs when the Network Service is enabled, and will be deprecating support completely in the future." Oct 1, 2019 at 23:21

Chrome removed almost all functionality of net-internals for some reason and it sounds like they removed the pac flag that you were using.

chromium docs link to this site that still lists the flag as valid.


  • 6
    Here's the related Chromium issue where file:// PAC files were removed: bugs.chromium.org/p/chromium/issues/…
    – paulcm
    Feb 18, 2019 at 12:45
  • 6
    Also, as suggested in the bug, you can also disable 'Enable Network Service' in chrome://flags to go back to the old behaviour that supports file:// pac files, though that will also be removed in future. Starting Chrome like /Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --disable-features=NetworkService has the same effect.
    – paulcm
    Feb 18, 2019 at 14:05
  • 2
    @paulcm that should be an answer. Feb 18, 2019 at 15:32

I know this is an old thread but it still ranks high in Google search results.

I'm still successfully using a local .pac file with Chrome and Chromium 97 in Linux. I'm running Chrome with the following:

--proxy-pac-url='data:application/x-javascript-config;base64,'$(base64 -w0 /path/to/local/proxy.pac)

This basically encodes the .pac file as base64 string and loads it as if it where some web response.

If you want to use this on Windows, see @TBGs answer

  • 1
    Thanks, this worked for me on Chromium 87.0
    – lsl
    Nov 24, 2020 at 6:46
  • 1
    This answer deserves more upvotes!
    – pst
    Jul 20, 2021 at 6:19
  • it din't work but thanks to this answer I could realize that a just need to move the .pac file to my lighttpd folder and point to there.
    – rodvlopes
    Jun 2 at 19:07
  • This still works in Chrome 102! Thanks! Jun 7 at 21:53

Unfortunately, Chrome plans to remove --disable-features=NetworkService and support for file:/// PAC URLs entirely in the future.

Here's the upstream bug (and specifically the comment marking WONTFIX): https://bugs.chromium.org/p/chromium/issues/detail?id=839566#c40

The solution that should work on Chrome 76+, without requiring an httpd, is to take the .zip file attached to that comment, unpack it somewhere permanent, and modify the bundled my_pac_script.js to be a symlink to your previous file:///... PAC file. Then install the extension in Chrome. It will load the PAC configuration when Chrome is started.


@jonny 's answer works like a charm ! (encoding proxy pac content to Base64)

However, if you're on Windows and have the same need, here's a small Powershell script you can use :

$proxyPacURL = "http://YOUR_URL/proxy.pac";
$proxyPacBytes = (Invoke-webrequest -URI $proxyPacURL).Content;
$proxyPacBase64 = [Convert]::ToBase64String($proxyPacBytes);
& 'C:\Program Files\Google\Chrome\Application\chrome.exe' --proxy-pac-url='data:application/x-javascript-config;base64,'$proxyPacBase64;
stop-process -Id $PID;

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