How can I get a debug log for the sites guest user/public profile? [updated for Spring 18]

Question

Normally, you can put debug monitoring on a user by name to see the details on the error they're getting (especially for the non-descript Error Loading a Visualforce Page).

But when you are trying to debug a site page, how do you get a debug log for the guest user?

Update

As of Spring '18 Salesforce has dropped the requirement to include the debug_logs cookie to get debug logs for the force.com site requests.

In Winter ’17, we introduced a change that required guest users to set browser cookies to activate debug logging. We had the best of intentions: All your public site visitors share one guest user license. Thus, when you enable logging for the guest user, the visitors’ collective activities can fill your debug logs quickly, hitting the log-size limit and causing log truncation. Sadly, people didn’t like the Winter ’17 change. Setting cookies is complicated, and the change made collecting debug logs for public users’ asynchronous activity impossible. We’ve seen the error of our ways. Your public users no longer need a debug_logs browser cookie to trigger logging. This change applies to both Lightning Experience and Salesforce Classic.

https://releasenotes.docs.salesforce.com/en-us/spring18/release-notes/rn_forcecom_debugging_guest_user.htm

Answer 1

Go to Environments>Logs>Debug log.

Where you would normally put the username, put the name of the Site.

For example: If your site is called MySite, enter MySite as the user name. Shockingly undocumented, but this gives you the debug you're looking for.

ATTENTION:

Winter17 is making a change to this--you'll now need to ALSO set a specific cookie in the guest user's browser to enable this.

https://releasenotes.docs.salesforce.com/en-us/winter17/release-notes/rn_forcecom_debugging_guest_user.htm#rn_forcecom_debugging_guest_user

Related Idea Exchange Idea for Integrations

The requirement for such a cookie is incompatible when building web-hook services for 3rd parties, there is an Idea Exchange post here to provide an IP whitelist as an alternative.

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Update from Spring '18 release notes:

In Winter ’17, we introduced a change that required guest users to set browser cookies to activate debug logging. We had the best of intentions: All your public site visitors share one guest user license. Thus, when you enable logging for the guest user, the visitors’ collective activities can fill your debug logs quickly, hitting the log-size limit and causing log truncation. Sadly, people didn’t like the Winter ’17 change. Setting cookies is complicated, and the change made collecting debug logs for public users’ asynchronous activity impossible. We’ve seen the error of our ways. Your public users no longer need a debug_logs browser cookie to trigger logging. This change applies to both Lightning Experience and Salesforce Classic.

Answer 2

Adding to Shane's answer-

The release notes which were linked to above include specific instructions for setting the cookie in Chrome, but not in Firefox. Here's one way of doing it in Firefox:

1. Install the Cookies Manager+ add-on
2. Create a cookie that looks like this:

Answer 3

Chrome & Edge

The above answers are not so clear instructions for winter 17 release .For winter 17 release open the public site first by clicking on the links in the Develop | Sites | Site

And once you are in the site, use Chrome developer console or Edge developer console and key in below

document.cookie ="debug_logs=debug_logs;domain=.force.com";

The help article does a good job of explaining this.

Answer 4

Update

This is no longer needed as of Spring '18

In Winter ’17, we introduced a change that required guest users to set browser cookies to activate debug logging. We had the best of intentions: All your public site visitors share one guest user license. Thus, when you enable logging for the guest user, the visitors’ collective activities can fill your debug logs quickly, hitting the log-size limit and causing log truncation. Sadly, people didn’t like the Winter ’17 change. Setting cookies is complicated, and the change made collecting debug logs for public users’ asynchronous activity impossible. We’ve seen the error of our ways. Your public users no longer need a debug_logs browser cookie to trigger logging. This change applies to both Lightning Experience and Salesforce Classic.

https://releasenotes.docs.salesforce.com/en-us/spring18/release-notes/rn_forcecom_debugging_guest_user.htm?edition=&impact=

Original

For API requests, i.e. webhooks, your only real option is a proxy to set this cookie.

I've got a node proxy working in our sandbox. I've made the repo public

var httpProxy = require('http-proxy');
var express = require('express');
var apiProxy = httpProxy.createProxyServer({target: process.env.TARGET, changeOrigin:true});
apiProxy.on('proxyReq', function(proxyReq, req, res, options) {
  proxyReq.setHeader('Cookie', 'debug_logs=debug_logs,domain=.force.com');
});
var addDebugCookie = function(req, res) {
  apiProxy.web(req, res);
};
var server = express();
server.all('/*', addDebugCookie);
var port = process.env.PORT || 5000;
server.listen(process.env.PORT || 5000)

Planning on setting this up on Heroku and then running all our webhook callbacks through this so we can turn on debug logs when something misbehaves.

UPDATE - we've started using this in production and everything is working fine so far, high level setup was:

• create a heroku app (or any other node.js hosting provider)
• deploy code to it
• set TARGET environmental variable to your force.com site
• update any callouts to use proxy url instead of force.com sites url

Answer 5

Another alternative to add cookies

Use Cookie Manager for chrome

Add like below screenshot

Answer 6

document.cookie = "debug_logs=debug_logs; path=/; domain=.force.com; value=debug_logs" ;

Add that to your page to set this cookie for the session.

Answer 7

I was messing around with the same in 2021 and the user was not popping up for Traced Entity Name in debug logs.

Did some findings and found that Salesforce has taken up back the process to inject cookie in web-browser in order to do enable the debug logs in the release of spring 18.

To trace the guest user, now we need to follow these simple steps to find the exact name of the guest user and then only we can create the debug logs on it as follows:

Reference

Note: if you are adding debug logs and you can figure out the actual user from the list of Traced Entity Name directly then you can make use of: *guest* in the search field, it will list all the guest users.