Jmeter	K6
In-built Protocols Support	HTTP FTP JDBC SOAP LDAP TCP JMS SMTP POP3 IMAP	HTTP 1.1 HTTP 2 WebSockets
Speed to write tests	Slow	Fast
Support of “Test as Code”	GUI oriented Possibility to create scripts, but too complex and lack of documentation Weak (Java) Hard to maintain	Scripts oriented JavaScript Easier to maintain
Ramp-up Flexibility	Plugins available to be able to configure flexible load	Supports ramp-up phases and flexible load
Test Results Analyzing	Yes	Yes
Resources Consumption	Heavy to run tests with multiple users on a single machine, more memory consumption	Lightweight and doesn’t take up so much memory of your machine
Easy to use with Version Control Systems	No	Yes
Number of Concurrent Users	Thousands, under restrictions	Thousands
Recording Functionality	Yes	No, but it allows to auto-generate a k6 script via an HAR file
Distributed Execution	Yes	Yes
Load Tests Monitoring	Add listeners, but consume more memory	No, logs through the console and paid version to get the K6 cloud reports, but you can send the metrics to other platforms

Jmeter is most used when:

• You need to perform a complex load including different protocols
• You can record scenarios
• Robust support and training ecosystem
• Require that a full scenario be written for every test
• If you need to simulate specific load with some custom ramp-up patterns
• If you just prefer UI desktop app for scripts creation, or you just do not know Javascript/YAML/JSON well enough

 

K6 solves some specific problems:

• CLI tool with developer-friendly APIs.
• You can use HAR files to generate record sessions
• Checks and Thresholds – for goal-oriented, automation-friendly load testing
• Open source, great support and documentation
• Lightweight uses Javascript
• Does not run in NodeJS and doesn’t run in a browser

 

Resources:

https://k6.io/