Fullstory Logging API

Implementation Files: This document covers core concepts. For code examples, see:

• SKILL-WEB.md — JavaScript/TypeScript (Browser)
• SKILL-MOBILE.md — iOS, Android, Flutter, React Native

Overview

Fullstory's Logging API allows developers to send log messages directly to Fullstory sessions. These logs appear in the session replay, providing valuable context for debugging user issues, tracking application state, and understanding user workflows—without cluttering the device's console or logging systems.

Key use cases:

• Error Context: Log errors with stack traces viewable in replay
• Application State: Record important state changes
• Debugging: Add contextual information during development
• Audit Trail: Log significant user actions
• Support Context: Add logs that support teams can see in sessions

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Core Concepts

Log Levels

All platforms support the same log levels, though the syntax differs:

Level	Use For	Severity
log	General information	Lowest
info	Informational messages	Low
warn	Warning conditions	Medium
error	Error conditions	High
debug	Debug information	Varies

Key Behaviors

Behavior	Description
Session-only	Logs appear in Fullstory session replay, not device console
Session context	Logs viewable in session replay timeline
Timestamped	Automatically timestamped by Fullstory
Searchable	Can search sessions by log content
String messages	All platforms require string messages

When to Use FS Logging vs Device Console

Use FS Logging	Use Device Console
Production errors you want in replay	Development-only debugging
State changes for support context	Verbose tracing during development
User action audit trails	Performance timing logs
Integration errors	Internal debugging
Customer-facing error context	CI/CD diagnostics

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Data Privacy

Never log sensitive data:

• ❌ Passwords, API keys, tokens
• ❌ Credit card numbers, CVVs
• ❌ Social Security numbers
• ❌ Personal health information
• ❌ Full email addresses (use user IDs instead)

Safe to log:

• ✅ User IDs (non-PII identifiers)
• ✅ Action names and types
• ✅ Error messages and codes
• ✅ Application state indicators
• ✅ Timing and performance metrics

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Best Practices

1. Use Appropriate Log Levels

debug   → Development troubleshooting, verbose details
log     → General operational information
info    → Significant but normal events
warn    → Potential issues, degraded functionality
error   → Failures requiring attention

2. Structure Log Messages Consistently

• Include context: action name, identifiers, state
• Use consistent prefixes for categorization: [Auth], [Payment], [API]
• Include relevant IDs for correlation
• Keep messages concise but informative

3. Log Strategically

Good to log:

• API failures and errors
• Authentication events (login/logout)
• Critical user actions (checkout, form submit)
• State transitions
• Third-party integration events

Avoid logging:

• Every mouse movement or scroll
• High-frequency events in loops
• Sensitive/PII data
• Redundant information

4. Create Centralized Logging Utilities

Build wrapper functions that:

• Add consistent formatting
• Include timestamps and context
• Check for Fullstory availability
• Sanitize potentially sensitive data

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Rate Limits and Constraints

Constraint	Limit
Message type	String only (no objects)
Rate limiting	Standard API rate limits apply
Excessive logging	May be throttled
Message length	Keep concise; very long messages may be truncated

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Common Patterns

Error Logging Pattern

1. Capture error details (message, type, stack)
2. Add context (action, state, identifiers)
3. Format as readable string
4. Send to Fullstory with error level
5. Optionally send to other error tracking services

Audit Trail Pattern

1. Define standard action format
2. Include timestamp, action name, details
3. Use info level for normal operations
4. Use warn for unusual but valid actions
5. Use error for failed operations

Integration Logging Pattern

1. Log connection attempts
2. Log successful connections
3. Log disconnections with reasons
4. Log errors with operation context
5. Log timeouts with duration

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Key Takeaways for Agent

When helping developers implement Fullstory logging:

1. Always emphasize:

   • Message format: Always pass strings, not objects or arrays
   • Privacy: Never log PII, passwords, or sensitive data
   • Log levels: Use appropriate severity levels
   • Frequency: Log significant events, not every operation

2. Common mistakes to watch for:

   • Logging objects instead of strings
   • Including PII in log messages
   • Excessive logging causing noise
   • Using wrong log levels

3. Platform routing:

   • Web (JavaScript/TypeScript) → See SKILL-WEB.md
   • iOS (Swift) → See SKILL-MOBILE.md § iOS
   • Android (Kotlin) → See SKILL-MOBILE.md § Android
   • Flutter (Dart) → See SKILL-MOBILE.md § Flutter
   • React Native → See SKILL-MOBILE.md § React Native

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Reference Links

• Web Logging: https://developer.fullstory.com/browser/fullcapture/logging/
• iOS Logging: https://developer.fullstory.com/mobile/ios/logging/
• Android Logging: https://developer.fullstory.com/mobile/android/logging/
• Help Center - Console Logs: https://help.fullstory.com/hc/en-us/articles/360020623154