Differences between Log4j and Log4j2
Differences between Log4j and Log4j2
Log4j (short for Logging for Java) is an open-source logging utility framework for Java applications, developed by the Apache Software Foundation. It allows developers to record application activity (debug messages, errors, warnings, etc.) in a structured and configurable way, making it easier to monitor and troubleshoot applications. Log4j was released in 2001. Widely adopted but now deprecated.
Log4j 1.x reached End-of-Life (EOL) in 2015 and is no longer maintained. Log4j2 is the successor and is actively maintained and secure. It is a complete rewrite (2014) with significant improvements in performance, flexibility, and security.
Differences
Some of the differences are as follows:
| Aspect | Log4j (1.x) | Log4j2 (2.x) |
|---|---|---|
| Release Year | 2001 | 2014 |
| Architecture | Monolithic | Modular (plugin system) |
| Configuration Formats | .properties, XML | .properties, XML, JSON, YAML |
| Asynchronous Logging | Not native (required custom appenders) | Built-in async logging (LMAX Disruptor) |
| Performance | Moderate | High (5-10x faster in some cases) |
| Automatic Reloading | Manual | Automatic configuration reloading |
| Lookups | Basic | Advanced (contextual data injection) |
| Java Version Support | Java 1.4+ | Java 8+ |
| Compatibility | N/A | Log4j 1.x API bridge available |
| Security | EOL (no security updates) | Actively maintained (CVE patches) |
| Community Support | Deprecated | Active development |
Important Security Note
Log4j2 had the critical Log4Shell vulnerability (CVE-2021-44228) in 2021, but updates (2.17.0+) contain fixes. Log4j 1.x is vulnerable to other CVEs and should NOT be used.
