Stack Overflow
Q&A for professional and enthusiast programmers
Cross Validated
Q&A for people interested in statistics, machine learning, data analysis, data mining, and data visualization
Super User
Q&A for computer enthusiasts and power users
Mathematics
Q&A for people studying math at any level and professionals in related fields
Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems
Ask Different
Q&A for power users of Apple hardware and software
Mathematica
Q&A for users of Wolfram Mathematica
Server Fault
Q&A for system and network administrators
Meta Stack Exchange
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Data Science
Q&A for Data science professionals, Machine Learning specialists, and those interested in learning more about the field
Web Applications
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Information Security
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Software Engineering
Q&A for professionals, academics, and students working within the systems development life cycle
Vi and Vim
Q&A for people using the vi and Vim families of text editors
English Language & Usage
Q&A for linguists, etymologists, and serious English language enthusiasts