bundlejs.com

What It Is

bundlejs is an online bundler and npm package size inspection tool for the JavaScript/npm ecosystem. It lets users enter a package name or code, build it, and view the output, console logs, and gzip/brotli-compressed size. Compared with traditional tools that only show package size, it emphasizes real build results with tree-shaking, and can also analyze the compressed size of external files such as CSS.

Core Capabilities

The tool works in a distinctive way: its FAQ states that the main bundler runs locally in the browser, using esbuild-wasm together with rollup to improve tree-shaking accuracy. As a result, when a build fails, users can see error messages that are closer to a real build workflow. It supports bundling multiple packages, tree-shaking by exported member, sharing via URL query parameters, compressed share links, and automatically bundling after opening a link. For analysis, interactive charts such as treemap, network, and sunburst can be enabled through configuration. Advanced configuration options include esbuild external, alias replacement, and loading modules from different sources such as unpkg, esm.sh, Skypack, jsDelivr, Deno, and GitHub raw.

Pricing and API

The captured text does not show any paid plans or payment methods, so it can currently be regarded as a free tool. An official API has been released and is available via deno.bundlejs.com and edge.bundlejs.com. It also supports generating badges, making it suitable for displaying package size information in a README. The API is sponsored by Upstash, but the text does not provide details on rate limits, SLA, or commercial support.

Pros and Cons

Its strengths are that it is straightforward to use, requires no local installation, and can quickly evaluate the size impact of npm dependencies. Local browser-based builds provide more transparent error feedback, while share links and badges are very practical for open-source library maintainers. The limitations are also fairly clear: tree-shaking depends on whether the CDN can access package.json, which may lead to version conflicts; some packages may require manual handling of default export; and alias currently does not consider the original package version, so replacement precision is limited.

Who It’s For and Access from China

It is suitable for frontend developers, npm package authors, and technical leads comparing dependency size during technology selection. It is also useful for open-source maintainers who want to display a bundle badge. The text does not specify access conditions from China; given that it relies on multiple overseas CDNs, the actual experience may be affected by network conditions. Alternatives include bundlephobia and bundlesize.com.