Which Programming Languages Are Dominating 2021? Insights from SlashData’s 19,000‑Developer Survey

A SlashData survey of more than 19,000 developers shows that JavaScript is now used by over 16.4 million developers worldwide, cementing its position as the most popular language in Q3 2021.

The 21st Global Developer Nation Report examined software‑developer trends in 160 countries during Q3 2021, covering programming languages, tools, APIs, applications, technology domains, and developers’ attitudes.

The report also explored developers’ participation in 5G and IoT projects, especially how programmers leverage new tools and services.

JavaScript’s continued popularity in both web and backend applications kept it at the top of the list, with more than 2.5 million new developers joining the JavaScript community in the past six months—an increase comparable to the entire Swift community and the combined communities of Rust and Ruby.

These figures also include language derivatives such as TypeScript and CoffeeScript.

Python follows closely, now used by roughly 11.3 million developers, primarily for data science, machine learning, and IoT development. Over the past 12 months Python added 2.3 million developers, reflecting a growth rate of about 25 %, one of the highest among all language communities.

Java remains the preferred language for mobile and desktop application development.

According to SlashData, the top five languages by developer count are C/C++ (7.5 million), PHP (7.3 million), and C# (7.1 million). PHP experienced the fastest growth in the last six months, gaining one million new developers, and, like JavaScript, remains popular for web and backend development.

Rust, an open‑source language mainly used for embedded software, “bare‑metal” development, and AR/VR game development, has seen the fastest growth of any language in the past 24 months, expanding from 400 k developers in Q3 2019 to 1.1 million.

The report highlights increasing developer involvement in 5G projects, especially those related to IoT, AR/VR, consumer electronics, and machine‑learning/AI.

China leads global 5G developer activity, with 13 % of Chinese respondents actively working on 5G projects—twice the global average. North America and South America follow with 11 % and 10 % respectively, though 43 % of North American developers report little or no interest in 5G.

Salary remains a primary driver for job changes: 50 % of developers cite higher pay as the main reason for switching employers, while 31 % each mention career development, skill expansion, and remote‑work opportunities. In Eastern Europe, nearly 70 % prioritize higher wages, and in China, about 60 % would change jobs for better compensation.

Experienced developers (16 + years) are less likely to switch, but those with three to five years of experience often seek more challenging roles, driving a peak in job changes.

Overall, while compensation is a significant factor, the report emphasizes that a range of motivations—including career growth, technology interest, and work‑life balance—shape developers’ employment decisions.