Code Quality Rank: L1
Programming language: C++
License: MIT
Tags: Logging    
Latest version: v1.8.1

spdlog alternatives and similar libraries

Based on the "Logging" category.
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  • G3log

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  • Boost.Log

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  • lwlog

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  • logog

    logog is a portable C++ library to facilitate logging of real-time events in performance-oriented applications, such as games. It is especially appropriate for projects that have constrained memory and constrained CPU requirements.
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  • xtr

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  • Serenity Logger

    Yet another Fast and Efficient logging framework. The goal is to be nanosecond level fast with extensibility (inspired by loggers such as spdlog, nanolog, and fmtlog and heavily influenced by the formatting used in fmtlib and <format>). This uses a built-in formatter that can be swapped out for <format> or fmtlib if desired.
  • templog

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Very fast, header-only/compiled, C++ logging library. ci  Build status Release


Header only version

Copy the include folder to your build tree and use a C++11 compiler.

Compiled version (recommended - much faster compile times)
$ git clone https://github.com/gabime/spdlog.git
$ cd spdlog && mkdir build && cd build
$ cmake .. && make -j

see example CMakeLists.txt on how to use.


  • Linux, FreeBSD, OpenBSD, Solaris, AIX
  • Windows (msvc 2013+, cygwin)
  • macOS (clang 3.5+)
  • Android

Package managers:

  • Debian: sudo apt install libspdlog-dev
  • Homebrew: brew install spdlog
  • MacPorts: sudo port install spdlog
  • FreeBSD: pkg install spdlog
  • Fedora: dnf install spdlog
  • Gentoo: emerge dev-libs/spdlog
  • Arch Linux: pacman -S spdlog
  • openSUSE: sudo zypper in spdlog-devel
  • vcpkg: vcpkg install spdlog
  • conan: spdlog/[>=1.4.1]
  • conda: conda install -c conda-forge spdlog
  • build2: depends: spdlog ^1.8.2


  • Very fast (see benchmarks below).
  • Headers only or compiled
  • Feature rich formatting, using the excellent fmt library.
  • Asynchronous mode (optional)
  • Custom formatting.
  • Multi/Single threaded loggers.
  • Various log targets:
    • Rotating log files.
    • Daily log files.
    • Console logging (colors supported).
    • syslog.
    • Windows event log.
    • Windows debugger (OutputDebugString(..)).
    • Easily extendable with custom log targets.
  • Log filtering - log levels can be modified in runtime as well as in compile time.
  • Support for loading log levels from argv or from environment var.
  • Backtrace support - store debug messages in a ring buffer and display later on demand.

Usage samples

Basic usage
#include "spdlog/spdlog.h"

int main() 
    spdlog::info("Welcome to spdlog!");
    spdlog::error("Some error message with arg: {}", 1);

    spdlog::warn("Easy padding in numbers like {:08d}", 12);
    spdlog::critical("Support for int: {0:d};  hex: {0:x};  oct: {0:o}; bin: {0:b}", 42);
    spdlog::info("Support for floats {:03.2f}", 1.23456);
    spdlog::info("Positional args are {1} {0}..", "too", "supported");
    spdlog::info("{:<30}", "left aligned");

    spdlog::set_level(spdlog::level::debug); // Set global log level to debug
    spdlog::debug("This message should be displayed..");    

    // change log pattern
    spdlog::set_pattern("[%H:%M:%S %z] [%n] [%^---%L---%$] [thread %t] %v");

    // Compile time log levels
    // define SPDLOG_ACTIVE_LEVEL to desired level
    SPDLOG_TRACE("Some trace message with param {}", 42);
    SPDLOG_DEBUG("Some debug message");

Create stdout/stderr logger object
#include "spdlog/spdlog.h"
#include "spdlog/sinks/stdout_color_sinks.h"
void stdout_example()
    // create color multi threaded logger
    auto console = spdlog::stdout_color_mt("console");    
    auto err_logger = spdlog::stderr_color_mt("stderr");    
    spdlog::get("console")->info("loggers can be retrieved from a global registry using the spdlog::get(logger_name)");

Basic file logger
#include "spdlog/sinks/basic_file_sink.h"
void basic_logfile_example()
        auto logger = spdlog::basic_logger_mt("basic_logger", "logs/basic-log.txt");
    catch (const spdlog::spdlog_ex &ex)
        std::cout << "Log init failed: " << ex.what() << std::endl;

Rotating files
#include "spdlog/sinks/rotating_file_sink.h"
void rotating_example()
    // Create a file rotating logger with 5mb size max and 3 rotated files
    auto max_size = 1048576 * 5;
    auto max_files = 3;
    auto logger = spdlog::rotating_logger_mt("some_logger_name", "logs/rotating.txt", max_size, max_files);

Daily files

#include "spdlog/sinks/daily_file_sink.h"
void daily_example()
    // Create a daily logger - a new file is created every day on 2:30am
    auto logger = spdlog::daily_logger_mt("daily_logger", "logs/daily.txt", 2, 30);

Backtrace support
// Debug messages can be stored in a ring buffer instead of being logged immediately.
// This is useful in order to display debug logs only when really needed (e.g. when error happens).
// When needed, call dump_backtrace() to see them.

spdlog::enable_backtrace(32); // Store the latest 32 messages in a buffer. Older messages will be dropped.
// or my_logger->enable_backtrace(32)..
for(int i = 0; i < 100; i++)
  spdlog::debug("Backtrace message {}", i); // not logged yet..
// e.g. if some error happened:
spdlog::dump_backtrace(); // log them now! show the last 32 messages

// or my_logger->dump_backtrace(32)..

Periodic flush
// periodically flush all *registered* loggers every 3 seconds:
// warning: only use if all your loggers are thread safe ("_mt" loggers)

// Stopwatch support for spdlog
#include "spdlog/stopwatch.h"
void stopwatch_example()
    spdlog::stopwatch sw;    
    spdlog::debug("Elapsed {}", sw);
    spdlog::debug("Elapsed {:.3}", sw);       

Log binary data in hex
// many types of std::container<char> types can be used.
// ranges are supported too.
// format flags:
// {:X} - print in uppercase.
// {:s} - don't separate each byte with space.
// {:p} - don't print the position on each line start.
// {:n} - don't split the output to lines.
// {:a} - show ASCII if :n is not set.

#include "spdlog/fmt/bin_to_hex.h"

void binary_example()
    auto console = spdlog::get("console");
    std::array<char, 80> buf;
    console->info("Binary example: {}", spdlog::to_hex(buf));
    console->info("Another binary example:{:n}", spdlog::to_hex(std::begin(buf), std::begin(buf) + 10));
    // more examples:
    // logger->info("uppercase: {:X}", spdlog::to_hex(buf));
    // logger->info("uppercase, no delimiters: {:Xs}", spdlog::to_hex(buf));
    // logger->info("uppercase, no delimiters, no position info: {:Xsp}", spdlog::to_hex(buf));

Logger with multi sinks - each with different format and log level

// create logger with 2 targets with different log levels and formats.
// the console will show only warnings or errors, while the file will log all.
void multi_sink_example()
    auto console_sink = std::make_shared<spdlog::sinks::stdout_color_sink_mt>();
    console_sink->set_pattern("[multi_sink_example] [%^%l%$] %v");

    auto file_sink = std::make_shared<spdlog::sinks::basic_file_sink_mt>("logs/multisink.txt", true);

    spdlog::logger logger("multi_sink", {console_sink, file_sink});
    logger.warn("this should appear in both console and file");
    logger.info("this message should not appear in the console, only in the file");

Asynchronous logging
#include "spdlog/async.h"
#include "spdlog/sinks/basic_file_sink.h"
void async_example()
    // default thread pool settings can be modified *before* creating the async logger:
    // spdlog::init_thread_pool(8192, 1); // queue with 8k items and 1 backing thread.
    auto async_file = spdlog::basic_logger_mt<spdlog::async_factory>("async_file_logger", "logs/async_log.txt");
    // alternatively:
    // auto async_file = spdlog::create_async<spdlog::sinks::basic_file_sink_mt>("async_file_logger", "logs/async_log.txt");   

Asynchronous logger with multi sinks
#include "spdlog/sinks/stdout_color_sinks.h"
#include "spdlog/sinks/rotating_file_sink.h"

void multi_sink_example2()
    spdlog::init_thread_pool(8192, 1);
    auto stdout_sink = std::make_shared<spdlog::sinks::stdout_color_sink_mt >();
    auto rotating_sink = std::make_shared<spdlog::sinks::rotating_file_sink_mt>("mylog.txt", 1024*1024*10, 3);
    std::vector<spdlog::sink_ptr> sinks {stdout_sink, rotating_sink};
    auto logger = std::make_shared<spdlog::async_logger>("loggername", sinks.begin(), sinks.end(), spdlog::thread_pool(), spdlog::async_overflow_policy::block);

User defined types
struct fmt::formatter<my_type> : fmt::formatter<std::string>
    auto format(my_type my, format_context &ctx) -> decltype(ctx.out())
        return format_to(ctx.out(), "[my_type i={}]", my.i);

void user_defined_example()
    spdlog::info("user defined type: {}", my_type(14));

User defined flags in the log pattern
// Log patterns can contain custom flags.
// the following example will add new flag '%*' - which will be bound to a <my_formatter_flag> instance.
#include "spdlog/pattern_formatter.h"
class my_formatter_flag : public spdlog::custom_flag_formatter
    void format(const spdlog::details::log_msg &, const std::tm &, spdlog::memory_buf_t &dest) override
        std::string some_txt = "custom-flag";
        dest.append(some_txt.data(), some_txt.data() + some_txt.size());

    std::unique_ptr<custom_flag_formatter> clone() const override
        return spdlog::details::make_unique<my_formatter_flag>();

void custom_flags_example()
    auto formatter = std::make_unique<spdlog::pattern_formatter>();
    formatter->add_flag<my_formatter_flag>('*').set_pattern("[%n] [%*] [%^%l%$] %v");

Custom error handler
void err_handler_example()
    // can be set globally or per logger(logger->set_error_handler(..))
    spdlog::set_error_handler([](const std::string &msg) { spdlog::get("console")->error("*** LOGGER ERROR ***: {}", msg); });
    spdlog::get("console")->info("some invalid message to trigger an error {}{}{}{}", 3);

#include "spdlog/sinks/syslog_sink.h"
void syslog_example()
    std::string ident = "spdlog-example";
    auto syslog_logger = spdlog::syslog_logger_mt("syslog", ident, LOG_PID);
    syslog_logger->warn("This is warning that will end up in syslog.");

Android example
#include "spdlog/sinks/android_sink.h"
void android_example()
    std::string tag = "spdlog-android";
    auto android_logger = spdlog::android_logger_mt("android", tag);
    android_logger->critical("Use \"adb shell logcat\" to view this message.");

Load log levels from env variable or from argv
#include "spdlog/cfg/env.h"
int main (int argc, char *argv[])
    // or from command line:
    // ./example SPDLOG_LEVEL=info,mylogger=trace
    // #include "spdlog/cfg/argv.h" // for loading levels from argv
    // spdlog::cfg::load_argv_levels(argc, argv);

So then you can:

$ export SPDLOG_LEVEL=info,mylogger=trace
$ ./example

Log file open/close event handlers
// You can get callbacks from spdlog before/after log file has been opened or closed. 
// This is useful for cleanup procedures or for adding someting the start/end of the log files.
void file_events_example()
    // pass the spdlog::file_event_handlers to file sinks for open/close log file notifications
    spdlog::file_event_handlers handlers;
    handlers.before_open = [](spdlog::filename_t filename) { spdlog::info("Before opening {}", filename); };
    handlers.after_open = [](spdlog::filename_t filename, std::FILE *fstream) { fputs("After opening\n", fstream); };
    handlers.before_close = [](spdlog::filename_t filename, std::FILE *fstream) { fputs("Before closing\n", fstream); };
    handlers.after_close = [](spdlog::filename_t filename) { spdlog::info("After closing {}", filename); };
    auto my_logger = spdlog::basic_logger_st("some_logger", "logs/events-sample.txt", true, handlers);        

Replace the Default Logger
void replace_default_logger_example()
    auto new_logger = spdlog::basic_logger_mt("new_default_logger", "logs/new-default-log.txt", true);
    spdlog::info("new logger log message");


Below are some benchmarks done in Ubuntu 64 bit, Intel i7-4770 CPU @ 3.40GHz

Synchronous mode
[info] **************************************************************
[info] Single thread, 1,000,000 iterations
[info] **************************************************************
[info] basic_st         Elapsed: 0.17 secs        5,777,626/sec
[info] rotating_st      Elapsed: 0.18 secs        5,475,894/sec
[info] daily_st         Elapsed: 0.20 secs        5,062,659/sec
[info] empty_logger     Elapsed: 0.07 secs       14,127,300/sec
[info] **************************************************************
[info] C-string (400 bytes). Single thread, 1,000,000 iterations
[info] **************************************************************
[info] basic_st         Elapsed: 0.41 secs        2,412,483/sec
[info] rotating_st      Elapsed: 0.72 secs        1,389,196/sec
[info] daily_st         Elapsed: 0.42 secs        2,393,298/sec
[info] null_st          Elapsed: 0.04 secs       27,446,957/sec
[info] **************************************************************
[info] 10 threads, competing over the same logger object, 1,000,000 iterations
[info] **************************************************************
[info] basic_mt         Elapsed: 0.60 secs        1,659,613/sec
[info] rotating_mt      Elapsed: 0.62 secs        1,612,493/sec
[info] daily_mt         Elapsed: 0.61 secs        1,638,305/sec
[info] null_mt          Elapsed: 0.16 secs        6,272,758/sec
Asynchronous mode
[info] -------------------------------------------------
[info] Messages     : 1,000,000
[info] Threads      : 10
[info] Queue        : 8,192 slots
[info] Queue memory : 8,192 x 272 = 2,176 KB 
[info] -------------------------------------------------
[info] *********************************
[info] Queue Overflow Policy: block
[info] *********************************
[info] Elapsed: 1.70784 secs     585,535/sec
[info] Elapsed: 1.69805 secs     588,910/sec
[info] Elapsed: 1.7026 secs      587,337/sec
[info] *********************************
[info] Queue Overflow Policy: overrun
[info] *********************************
[info] Elapsed: 0.372816 secs    2,682,285/sec
[info] Elapsed: 0.379758 secs    2,633,255/sec
[info] Elapsed: 0.373532 secs    2,677,147/sec


Documentation can be found in the wiki pages.

Thanks to JetBrains for donating product licenses to help develop spdlog

*Note that all licence references and agreements mentioned in the spdlog README section above are relevant to that project's source code only.