EasyLogger is an ultra-lightweight, high-performance C/C++ logging library with a footprint under 1.6 KB of ROM and 0.3 KB of RAM, aimed at embedded and resource-constrained developers who need structured, filterable logs on devices where a full logging framework will not fit.

What it is

EasyLogger is a C/C++ log library built for small embedded targets, with an MIT licence and roughly 4,749 stars and 1,316 forks on GitHub. Its defining property is size: the README states ROM under 1.6K and RAM under 0.3K, which places it in the class of libraries intended for microcontrollers rather than servers. It lives in the embedded C ecosystem and is ported by the user onto a target board; the library ships a demo under demo/os/rt-thread/stm32f10x/ and Chinese-language documentation under docs/zh/, including a kernel API document and a porting document. Log levels follow Android Logcat conventions, from level 0 (Assert) down to level 5 (Verbose), and the level set is [A], [E], [W], [I], [D] and [V].

The concrete problem it solves is that logging is normally the first thing a firmware author drops, because printf-style output through a UART is unstructured and any richer logging library costs flash and RAM that the device does not have. EasyLogger replaces ad-hoc print statements with a levelled, tagged, filterable logger that stays inside a tiny memory budget. It also decouples the logger core from the output destination, so the same library can write to a terminal, to a file system, or directly to flash memory through the EasyFlash library without a file system being present. Configuration is deliberately simple: parameters and output are a singleton, meaning exactly one global configuration applies, which keeps the software small but means it cannot support complex multi-sink output arrangements.

Key capabilities

• Filtering by tag, level, and keyword, so noisy logs can be narrowed at runtime; RAW and hexdump format logs do not support tag or keyword filtering.
• Static output levels set at compile time through macros, plus dynamic levels controlled at runtime through the API.
• Independently configurable output format per level: level, time, tag, process information, thread information, file path, line number, and method name.
• Per-level colour and font styling set in elog_cfg.h.
• A Flash plugin that stores logs through the EasyFlash interface with no file system required, and supports reading back historical logs after a reboot.
• A File plugin supporting file archiving and circular file storage, rolling to a new file once a configured size is exceeded.
• Async output, listed as completed in the roadmap, which removes the runtime slowdown caused by synchronous logging on slow platforms.

Who uses it and how

• Firmware developers on small embedded devices without a file system, who store logs in flash via EasyFlash and read them back after restart.
• Teams running RT-Thread on STM32F10x hardware, using the shipped demo at demo/os/rt-thread/stm32f10x/ as the porting starting point.
• Devices with a console or terminal attached, where dynamic filtering and level switching let an engineer change log verbosity without reflashing.
• Systems with a file system, where the File plugin handles capacity-based rotation so long-running logs do not exhaust storage.

Getting started

There is no published package or container image; integration means taking the source, reading the documentation under docs/zh/ first, and porting the library to the target, with the RT-Thread STM32F10x demo as the working reference. The porting guides are docs/zh/port/kernel.md for the core and docs/zh/port/flash.md for the flash plugin.

How it compares

No alternative logging products are named in the available facts, and no list of paid products is provided. Android Logcat appears only as the reference for the numbering of log levels, not as a competing library. On the evidence given, EasyLogger stands alone in this registry.

When to use it — and when not to

A self-hoster must operate the porting work directly: there is no package manager install, the docs are written in Chinese, and the singleton configuration limits the design to one global output setup, so anyone needing several independent log sinks with different formats should look elsewhere. The flash-backed storage path also depends on porting EasyFlash separately. It remains a reasonable choice when flash and RAM are the binding constraint and structured, filterable logs are worth the porting effort.

0.[A]：断言(Assert)
1.[E]：错误(Error)
2.[W]：警告(Warn)
3.[I]：信息(Info)
4.[D]：调试(Debug)
5.[V]：详细(Verbose)