Configuring Xcode 8+ to Hide Unwanted System Logs

Problem Background

When creating new blank projects in Xcode 8 and later versions, running the application generates numerous system logs in the console. These logs originate from various iOS subsystems, such as:

2016-06-13 16:33:34.406093 TestiOS10[8209:100611] bundleid: com.appc.TestiOS10, enable_level: 0, persist_level: 0, propagate_with_activity: 0
2016-06-13 16:33:34.406323 TestiOS10[8209:100607] Created DB, header sequence number = 248
2016-06-13 16:33:34.409564 TestiOS10[8209:100611] subsystem: com.apple.UIKit, category: HIDEvents, enable_level: 0, persist_level: 0, default_ttl: 0, info_ttl: 0, debug_ttl: 0, generate_symptoms: 0, enable_oversize: 0, privacy_setting: 0

While these logs are valuable for system debugging, they significantly interfere with developers' ability to view their own NSLog or print outputs during daily development work.

Solution 1: Complete Activity Log Disable

The simplest solution involves setting an environment variable to disable these system logs:

1. From the Xcode menu, open: Product > Scheme > Edit Scheme
2. In Environment Variables, set OS_ACTIVITY_MODE = disable

This configuration completely disables system activity log output, allowing the console to display only the developer's own log information.

Solution 2: Simulator-Specific Configuration

For more granular control, you can configure the system to disable logs only in the simulator while preserving them on physical devices:

1. In Product > Scheme > Edit Scheme... > Run (Debug), set the OS_ACTIVITY_MODE environment variable to ${DEBUG_ACTIVITY_MODE}
2. Navigate to project build settings and add a user-defined setting named DEBUG_ACTIVITY_MODE
3. Expand this setting and click + next to Debug to add a platform-specific value
4. Select the dropdown and change it to "Any iOS Simulator", then set its value to "disable"

With this configuration, system logs won't appear when running in the simulator, while full log information remains available during device execution.

Technical Principle Analysis

These system logs originate from iOS's Unified Logging System, which provides structured logging capabilities. The OS_ACTIVITY_MODE environment variable controls the behavior of this logging system:

• When set to disable, the system suppresses most debugging and diagnostic log outputs
• By default, the system outputs log information at all levels
• This configuration only affects system logs and doesn't impact developers' own NSLog or print statements

Best Practice Recommendations

In practical development, we recommend:

• Use Solution 2 during development phases to maintain clean output in the simulator
• Preserve complete system logs during physical device debugging for problem diagnosis
• No configuration is needed for production versions, as system logs are optimized by default in release builds