QOS.CH Sarl (Switzerland)

QOS.ch Sarl (Switzerland) is a software design and development company based in Vouvry, Switzerland. Our company has experience building mission-critical enterprise software using the Java language.

We are founding contributors of several open source projects, namely log4j 1.x, reload4j, slf4j and logback. We also offer professional support for these projects.

Professional Support

Although the quality of support for various open source projects can be good, most are operated on a best-effort basis. If you require authoritative responses and guaranteed response times, then please read on.

As the founder of log4j 1.x, SLF4J and logback projects, we offer support services for these project. The base support package entails guaranteed response times. Just as importantly, it includes a review of your logging practices. Such reviews often result in considerable savings in reduced infrastructure costs. We also offer custom development services.

For more information about our support package please contact us. We will be happy to provide further details and discuss your specific needs.

Donations and sponsorships

You can also support SLF4J/logback projects via donations and sponsorship. We thank our current supporters and sponsors for their continued contributions.


Email:   sales(at)qos.ch
Postal Address:   QOS.ch Sàrl
  rue Arthur Parchet 1
  CH-1896 Vouvry (VS)

Prevalence of logging frameworks

Regarding the log4shell vulnerability, the prevalence of various java logging libraries puts things into perspective. Here are the relevant figures as found in mvnrepository site on 2021-12-17.

Project Category group:artifact usageCount percentage
SLF4J API org.slf4j:slf4j-api 52,247 69%
Commons-logging API commons-logging:commons-logging 10,412 14%
SLF4J API org.slf4j:jcl-over-slf4j 7,546 10%
LOG4J2 API org.apache.logging.log4j:log4j-api 5,226 7%
Total API - 75,431 100%
Project Category group:artifact usageCount percentage
LOGBACK implementation ch.qos.logback:logback-classic 21,770 48%
LOG4J1 implementation log4j:log4j 16,610 37%
LOG4J2 implementation org.apache.logging.log4j:log4j-core 6,974 15%
Total implementaion - 45,174 100%

Notwithstanding its 48% prevalence overall (in the implementation category), no attacks have been reported against logback that we are aware of.