Bun vs Deno for Solo Developers

Quick Comparison

Bun Overview

Bun is the speed-focused JavaScript runtime, historically built in Zig and now mid-migration to Rust, running on JavaScriptCore. It is designed as an all-in-one toolkit: runtime, bundler, package manager, test runner, and TypeScript handler in one binary. The whole pitch is performance and developer experience improvements over Node. In December 2025 the Bun team joined Anthropic, with the project staying open source under the MIT license, so the runtime now has a well-funded backer behind it.

Bun targets Node compatibility aggressively. It reads package.json, installs from npm, supports CommonJS and ES modules, and implements most Node built-in modules. The goal is "Node, but faster and with batteries included." If you know Node, you know Bun.

For solo devs, Bun is appealing because the iteration loop is faster, the toolchain is unified, and the migration cost from Node is low. You don't need to learn new APIs or restructure your imports. You just swap node for bun and most things work.

Deno Overview

Deno is the security-first, web-standards-first JavaScript runtime created by Ryan Dahl (also Node's creator). Deno was built to fix the things Dahl regretted about Node: the lack of security, the divergence from web standards, the npm-centric module system.

The original Deno used URL-based imports instead of npm, ran with explicit permission flags (no filesystem or network access without --allow-read or --allow-net), and shipped with TypeScript as a first-class citizen. Web standards like fetch, WebSocket, and Web Crypto were the runtime APIs, not third-party modules.

Deno 2, released in late 2024, was the pragmatism update. Full npm compatibility (you can deno install npm:react), package.json support, node_modules folder support, and a workspaces system. The web standards stayed, but the "no npm" stance softened to "npm works, but JSR is recommended."

Key Differences

Engine choice has performance implications. Bun uses JavaScriptCore, the engine in Safari. Deno uses V8, the engine in Chrome and Node. V8 is more aggressively optimized for long-running server workloads. JavaScriptCore has faster startup. For short-lived tasks like CLI tools or serverless functions, Bun usually wins. For long-running servers under load, the performance is close, sometimes V8 (Deno) wins.

Security model is the biggest philosophical difference. Deno requires explicit permission flags to access the network, filesystem, or environment variables. deno run server.ts won't access disk unless you pass --allow-read. This is genuinely safer for running untrusted code, like a script someone sent you. Bun trusts your code by default, the same as Node. For your own apps the security model rarely matters; for third-party scripts it does.

npm compatibility maturity. Both support npm now. Bun has had npm-native compatibility from day one and handles most edge cases. Deno 2's npm support is solid but newer, and some packages still hit compatibility issues. If you're depending on a finicky npm package with native modules, Bun is more likely to work without fuss.

Web standards adoption. Deno wins here. The runtime APIs ARE web standards including fetch, FormData, URL, WebSocket, ReadableStream, Web Crypto. Code you write for Deno often runs in browsers and Cloudflare Workers with no changes. Bun implements web standards too but with more Node-flavored polyfills mixed in.

Tooling unification. Both ship as single binaries with built-in TypeScript, test runners, bundlers, and formatters. Bun's formatter is fast but young; Deno's formatter (basically dprint) is mature. Both have task runners. Deno's permissions integrate with the runtime; Bun's tooling assumes trusted code.

Hosting and edge runtimes. Bun and Deno both run on most modern platforms. Deno has Deno Deploy, a first-party edge runtime that's basically Cloudflare Workers but Deno-flavored. Bun runs anywhere a Linux binary runs. For serverless specifically, Deno Deploy is more mature than Bun's serverless story.

By the Numbers (2026)

The marketing copy on both sites is hard to compare apples to apples, so here are the real figures, all checked on 2026-05-28.

Versions and cadence. Bun's latest release is 1.3.14, published on 2026-05-13. Deno's latest is 2.8.1, published on 2026-05-27. Bun reached 1.0 in September 2023; Deno 2 landed in early October 2024 and is the version that brought the npm and package.json compatibility this whole comparison hinges on.

Adoption. Bun has roughly 92,600 GitHub stars on the oven-sh/bun repository. Deno has roughly 106,900 stars on denoland/deno, which makes sense given Deno is the older project (created in 2018 versus Bun's 2021). On npm, the bun installer package pulled about 1.76 million downloads in the week of 2026-05-21 to 2026-05-27, while the deno installer package pulled about 56,000 in the same window. Read that gap with care. Most Deno users install through the official shell script or a package manager rather than the npm wrapper, so the npm number badly understates Deno's real footprint. It is a signal that Bun is the one people reach for as a project-local dependency, not a clean popularity ranking.

Engine and implementation. Bun runs on JavaScriptCore, the engine in Safari, and is written across Rust, Zig, and C++ while the team migrates the codebase from Zig to Rust (a rewrite that began in 2026 and reportedly already passes the existing test suite). Deno runs on V8, the engine in Chrome and Node, and is written in Rust.

Cost. Both runtimes are free and MIT licensed, so the binaries cost nothing either way. The pricing difference shows up in first-party hosting. Bun has no first-party hosting product; you deploy the binary anywhere a Linux process runs. Deno sells Deno Deploy, its edge platform, with a real free tier and paid tiers above it.

Real Cost at Solo-Dev Scale

Since the two only differ on price through hosting, here is what that actually looks like for a typical solo project. Pricing is current as of 2026-05-28.

The workload. Assume a small backend or edge API that serves 1.5 million requests a month, moves about 15 GB of egress, and burns well under 15 hours of CPU time. That is a realistic shape for a paid side project or an early product with a few hundred active users.

On Bun. The runtime is free, so your bill is whatever your host charges. A single small VPS that comfortably runs a Bun process sits in the five to ten dollars a month range, and that figure is set by your provider, not by Bun. Bun itself never appears on the invoice.

On Deno via Deno Deploy. That same workload fits inside the Deno Deploy free tier, which covers 1 million requests, 20 GB of bandwidth, and 15 hours of CPU time. At 1.5 million requests you cross the free request ceiling, so on the Pro plan at $20 a month you get 5 million requests and 200 GB included, leaving plenty of headroom. So the honest answer is that Deno Deploy is $0 a month right up until you pass 1 million requests, then it is $20 a month flat until you are well into the millions.

The takeaway. Neither runtime charges you for itself. The decision is whether you want to manage a box (the Bun path, cheapest at the bottom, your time is the cost) or hand hosting to a managed edge platform (the Deno Deploy path, free until real traffic, then a predictable $20). If you would self-host Deno on the same VPS instead of using Deploy, the two converge to the identical "cost of one small server" outcome.

When to Choose Bun

• You're migrating from Node and want minimal friction
• You need every existing npm package to work
• Speed and toolchain unification matter most
• You're building with Elysia or other Bun-native frameworks
• You want one binary that does everything

When to Choose Deno

• Security model matters (running untrusted scripts, multi-tenant code)
• You're writing code that should also run in browsers or Workers
• You want JSR's typed module registry over npm
• You're deploying to Deno Deploy or Supabase Edge Functions
• Web standards alignment matters for portability

The Verdict

Both are good in 2026 and the gap between them keeps shrinking. The choice often comes down to what you care about more: performance and Node compatibility, or web standards and security.

For solo devs migrating from Node and wanting the fastest path to working code, Bun is the easier transition. Your existing knowledge transfers almost completely. Your packages mostly just work. The toolchain is unified and the speed is real.

For solo devs starting fresh, especially if you want code that's portable across runtimes (Workers, browsers, Deno Deploy), Deno has the better foundation. Writing to web standards once and running everywhere is genuinely useful, and Deno 2 made the npm friction mostly disappear.

If you're undecided, default to Bun for backend APIs and CLI tools where performance matters and you want Node-style ecosystem access. Default to Deno when you're writing code that should run in multiple environments or when you're building security-sensitive scripts. Both runtimes are far enough along that you won't regret either choice.

Sources

All figures checked on 2026-05-28.

• Bun GitHub repository and star count: https://github.com/oven-sh/bun
• Bun latest release (1.3.14): https://github.com/oven-sh/bun/releases/latest
• Bun homepage and feature claims: https://bun.com/
• Bun joins Anthropic, stays MIT licensed (Dec 2, 2025): https://bun.com/blog/bun-joins-anthropic
• Bun language, engine, history, and Rust rewrite: https://en.wikipedia.org/wiki/Bun_(software)
• Bun npm download stats: https://api.npmjs.org/downloads/point/last-week/bun
• Deno GitHub repository and star count: https://github.com/denoland/deno
• Deno latest release (2.8.1): https://github.com/denoland/deno/releases/latest
• Deno 2 announcement and npm compatibility: https://deno.com/blog/v2.0
• Deno Node and npm compatibility docs: https://docs.deno.com/runtime/fundamentals/node/
• Deno Deploy pricing tiers and limits: https://deno.com/deploy/pricing
• Deno npm download stats: https://api.npmjs.org/downloads/point/last-week/deno