By ByteBot
The 2025 JetBrains Developer Ecosystem Survey introduces the “Promise Index”—a new metric measuring which programming languages developers believe have the highest growth potential. TypeScript leads this index, yet Rust shows the fastest actual growth on GitHub at 89% year-over-year compared to TypeScript’s 43%. Meanwhile, Rust jumped from #17 to #8 on the TIOBE Index in just one year. The paradox: TypeScript represents what developers THINK will grow, while Rust demonstrates what IS growing.
What the Promise Index Measures (And Why TypeScript Leads)
JetBrains’ Promise Index combines audience growth over the past five years, the stability of that growth, the percentage of developers planning to adopt the language, and the proportion of current users who intend to stay versus switch. TypeScript tops this ranking because it’s experienced the most dramatic real-world usage rise over five years, becoming GitHub’s #1 most-used language in August 2025.
The survey data is substantial: 24,534 developers across 194 countries (JetBrains) plus 49,000+ responses (Stack Overflow). TypeScript now has 12.5 million GitHub repositories with 43% year-over-year growth and 2.6 million active contributors—the largest contributor base of any language. Additionally, 69% of developers use TypeScript for large-scale web applications.
Related: TypeScript Overtakes Python as GitHub’s Most-Used Language
The Promise Index reveals what developers BELIEVE is worth learning, which drives education curricula, bootcamp content, and hiring trends. However, it measures future sentiment and growth potential—not current adoption velocity. That’s where the paradox begins.
Rust’s Reality Exceeds Its Promise: 89% Growth Leads the Pack
Rust ranks #2 on the Promise Index, but it’s showing the HIGHEST actual growth among major programming languages. With 89% GitHub repository growth compared to TypeScript’s 43% and Python’s 31%, Rust’s adoption is accelerating faster than developers’ perceptions suggest. The language jumped from #17 to #8 on the TIOBE Index in a single year—a nine-position leap that’s nearly unprecedented.
Enterprise adoption tells the same story. Forty-five percent of organizations now use Rust in production environments, up seven percentage points from 2023. Commercial Rust usage increased 68.75% between 2021 and 2024, with 38% of Rust developers now using it for the majority of their work. The language has maintained an 83% favorability rating for nine consecutive years—the highest in the industry.
What’s driving this explosion? Security mandates from the US Government recommending memory-safe programming, plus enterprise requirements for replacing C and C++ in security-critical systems. Rust delivers C-level performance without memory safety bugs, making it ideal for operating systems, browsers, infrastructure tools, and embedded devices. This isn’t hype—it’s market demand for systems programming that doesn’t crash.
Why the Gap Isn’t a Paradox—It’s Market Segmentation
TypeScript and Rust aren’t competing. They serve fundamentally different markets with distinct growth curves, and understanding this segmentation prevents costly career missteps.
TypeScript owns web development: frontend applications, fullstack frameworks like Next.js, Node.js backend services, and serverless platforms (Vercel, Cloudflare Workers, AWS Lambda). The language has a 2-4 week learning curve for JavaScript developers and offers type safety without enterprise boilerplate. Its promise reflects continued dominance in an already-captured market—web development isn’t expanding as fast as it was five years ago.
Rust targets systems programming: operating systems (Linux kernel), cloud infrastructure (AWS services), security-critical applications, and performance-intensive workloads. The learning curve is steeper (2-4 months to comfort while “fighting the borrow checker”), but the payoff is massive. Systems programming and security represent vast, largely untapped markets where C and C++ still dominate despite their memory safety flaws. Rust’s explosive growth signals the BEGINNING of this replacement cycle, not its peak.
Related: Niche Language Premium: 2% Adoption, 38% Top Earners
The “paradox” resolves when you recognize that the Promise Index measures sentiment about future growth WITHIN CURRENT MARKET CONTEXTS. TypeScript developers see continued web expansion. Rust developers see untapped systems programming opportunities. Both are correct for their respective markets.
What This Means for Your 2025-2026 Learning Roadmap
Career planning requires matching languages to target markets, not chasing rankings. TypeScript’s #1 Promise ranking reflects its maturity and market saturation. It’s the safe bet for web development jobs because it already dominates that space. Rust’s #2 Promise ranking with 89% actual growth reveals early adoption—the systems programming market is massive but still mostly using unsafe C and C++.
Survey data on languages developers plan to adopt next reinforces this split: Go (11%), Rust (10%), Python (7%), Kotlin (6%), and TypeScript (6%). Notice that TypeScript ranks fifth in adoption intentions despite leading the Promise Index. Developers aren’t rushing to learn TypeScript because many already know it—it’s the most-used language on GitHub.
For immediate job opportunities, TypeScript wins. The web development market is the largest in software, and TypeScript is the de facto standard. However, growth trajectory favors Rust. As enterprises replace C and C++ for security reasons, Rust skills become increasingly valuable. The timeline differs: TypeScript offers quick entry and immediate returns, while Rust requires longer investment but targets faster-growing segments.
The smart play? Learn both. Master TypeScript for frontend and fullstack work, then add Rust for performance-critical modules via WebAssembly (browser) or napi-rs (Node.js). This “full spectrum engineer” approach maximizes career versatility—you can build interfaces AND infrastructure, web apps AND systems tools.
Key Takeaways
- The Promise Index measures what developers BELIEVE will grow, not what IS growing fastest—TypeScript leads in perceived potential, Rust leads in actual adoption velocity at 89% year-over-year
- Market segmentation explains the gap: TypeScript dominates maturing web development (already #1 on GitHub), while Rust targets early-stage systems programming replacement of C/C++
- Enterprise momentum favors Rust for long-term growth: 45% production usage, 68.75% commercial increase since 2021, driven by security mandates and memory safety requirements
- Career ROI depends on target market and timeline—TypeScript offers immediate web jobs in the largest market, Rust offers future-proofing in the fastest-growing segment (systems and security)
- The optimal strategy is learning both languages for full spectrum versatility: TypeScript for business logic and web layers, Rust for performance-critical modules via WebAssembly or native integrations
