https://help.salesforce.com/s/articleView?id=sf.code_debug_log.htm&language=en_US&type=5
A debug log includes a header, execution units, code units, log lines, and other log data. Which events are logged depends on various factors. These factors include your trace flags, the default logging levels, your API header, user-based system log enablement, and the log levels set by your entry points.

https://help.salesforce.com/s/articleView?id=000392579&language=en_US&type=1
Debug logs allow you to see exactly what is happening when Salesforce is executing your business logic. This guide will help you capture a debug log to analyze. Resolution. Turn on Debug Logs. 1. Open Salesforce Setup . 2. Search Debug in the quick find. 3.

https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_debugging_debug_log.htm
If logging is enabled when classes or triggers execute, logs are generated at the time of execution. To view a debug log from Setup, enter Debug Logs in the Quick Find box, then select Debug Logs. Then click View next to the debug log that you want to examine. Click Download to download the log as an XML file.

https://help.salesforce.com/s/articleView?id=sf.code_debug_log_details.htm&language=en_US&type=5
To view, retain, and delete debug logs: View All Data. After you generate a debug log, the type and amount of information listed depends on the filter values you set for the user. However, the format for a debug log is always the same. Note Session IDs are replaced with "SESSION_ID_REMOVED" in Apex debug logs.

https://trailhead.salesforce.com/content/learn/modules/developer_console/developer_console_logs
After execution, double-click the log that appears in the Logs tab. Let's try the first method. Select Debug | Open Execute Anonymous Window. The Enter Apex Code window displays the last code that you entered for execution. If it's different from the following code, delete it and paste the following code.

https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_debugging_system_log_console.htm
Use this tool to inspect debug logs that include database events, Apex processing, workflow, and validation logic. To learn more about working with logs in the Developer Console, see Log Inspector in the Salesforce online help. When using the Developer Console or monitoring a debug log, you can specify the level of information that gets

https://admin.salesforce.com/blog/2020/how-i-solved-this-dive-deep-into-the-debug-log
How I solved it. I used the debug log to compare what happens when I load our Scheduling Form, which is a Force.com site that displays volunteer slots and data for determining schedule preferences. This helped me (1) understand what the code does every step of the way and (2) find the problem! 1. Zoom in on the problem.

https://trailhead.salesforce.com/content/learn/projects/find-and-fix-bugs-with-apex-replay-debugger/apex-replay-debugger-debug-your-code
When replaying a debug log, make sure that your Salesforce DX project contains the same Apex source code that generated the debug log. Otherwise, line numbers and variables referenced by the debugger might lead you to confusion instead of to discoveries. The debug log must be generated with a log level of FINER or FINEST for log category

https://trailhead.salesforce.com/content/learn/modules/apex_basics_dotnet/debugging_diagnostics
Position your cursor over line 10 in the left margin and click once. A red dot appears next to the line number. Double-click the latest entry in the Logs panel to open the debug log. Select Debug > Open Execute Anonymous Window . Delete the existing code, and insert the following snippet:

https://help.salesforce.com/s/articleView?id=sf.code_setting_debug_log_levels.htm&language=en_US&type=5
A debug level is a set of log levels for debug log categories, such as Database, Workflow, and Validation. A trace flag includes a debug level, a start time, an end time, and a log type. The log types are DEVELOPER_LOG, USER_DEBUG, and CLASS_TRACING. When you open the Developer Console, it sets a DEVELOPER_LOG trace flag to log your activities

https://www.salesforceben.com/easily-debug-salesforce-using-nebula-logger/
System debug logs are retained for 24 hours. Debug logs are retained for seven days. Reporting and monitoring of logs is very limited. Paid add-ons (like Salesforce Shield) or third-party tools are typically needed for more detailed reporting and monitoring. These limits can make it difficult to rely solely on Salesforce's logging to

https://developer.salesforce.com/docs/atlas.en-us.sfdx_dev.meta/sfdx_dev/sfdx_dev_develop_view_apex_debug_logs.htm
In Salesforce Extensions for VS Code, prepare the org to generate logs and configure the debugger. For Replay Debugger, run SFDX: Turn on Apex Debug Log for Replay Debugger. Create a launch configuration file for Replay Debugger or Interactive Debugger. After you run the tests, get a list of the debug logs. View a debug log by passing its ID to

https://salesforce.stackexchange.com/questions/8480/where-can-i-read-the-debug-output-of-test-classes
Launch your Devloper Console (Username>Developer Console) Go to Setup>Developer>Apex Test Execution>Select Tests> pick the testing class you want to see the debug logs from can click run. Go to your Dev Console. In the logs section you will see the ApexTestHandler operation. Double click that log.

https://www.saasguru.co/debug-logs-in-salesforce/
1. Accessing Debug Logs: Navigating to the Debug Logs page: From Salesforce Setup, enter "Debug Logs" in the Quick Find box. Select "Debug Logs" from the dropdown to access the logs page. Setting up debug log filters: Use the 'New' button to create a new Trace Flag. Specify which user or class you want to monitor.

https://developer.salesforce.com/tools/vscode/en/apex/replay-debugger
Replay Debug Logs. Replay your debug log and inspect your variables' values. To switch to VS Code's Debug view, click the bug icon on the left edge of the window. To replay the code execution that was logged in your debug log until you hit your first breakpoint, click the green play icon in the Debug actions pane at the top of the editor.

https://hevodata.com/learn/salesforce-debug-logs/
Let's see how to view your Salesforce debug logs: To view the debug logs, from the setup option in Salesforce, enter 'Debug Logs' in the 'Quick Find box', then select 'Debug Logs'. Once you select the Debug Logs, click the 'View' button to examine the log. Click 'Download' to download the logs as an XML file.

https://bluecanvas.io/blog/debugging-apex-salesforce-debug-log-checkpoints
Trace Flags in Salesforce allow you to specify which user's activity should be logged in the Debug Logs. To set up a Trace Flag, go to Setup and search for "Debug Logs." Click on "New Trace Flag" and specify the user for whom you want to capture logs. Additionally, you need to set the Debug Level, which determines the logging granularity.

https://help.salesforce.com/s/articleView?id=sf.code_debug_log_delete.htm&language=en_US&type=5
To view, retain, and delete debug logs: View All Data. Open Developer Console. At the bottom of the console, select the Query Editor tab. Select Use Tooling API. Enter this SOQL query: SELECT Id, StartTime, LogUserId, LogLength, Location FROM ApexLog. Click Execute. Select the logs you want to delete.

https://help.salesforce.com/s/articleView?id=sf.code_monitoring_debug_logs.htm&language=en_US&type=5
Set trace flags to trigger logging for users, Apex classes, and Apex triggers in the Developer Console or in Setup. Monitor the resulting logs to diagnose

https://www.salesforce4ever.com/catch-logs-from-your-api-user-thanks-to-automations-and-event-monitoring/
Use the standard Salesforce Debug Logs feature on the API user to catchs the logs. Setting a debug log on your integration user will catch all declarative actions and custom code that are triggered by the API call. This is therefore more relevant to inbound API calls to Salesforce than outbound calls. Pros.

https://help.salesforce.com/s/articleView?id=000382222&language=en_US&type=1
Please follow the steps below to setup the Logs if you're unsure how to do so. 1. Turn on Debug Logs. Once logged into the Sales/Service Cloud. Select Setup. In the Quick Find, search for Debug Logs. Select Debug Logs. Next to User Trace Flag click New. Set Traced Entity Type = User.