Can I Use
caniuse.com
Answers whether a browser feature is safe to ship yet
No sign-upClassic
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bundlephobia.com
Shows what an npm package costs your bundle before you install it.
Type a package name and it reports minified and gzipped size, estimated download time on 3G and 4G, which dependencies contribute most of the weight, and whether the package is tree-shakeable. Comparing two candidate libraries takes about fifteen seconds and regularly changes the decision. Results come from a cached analysis, so a version published minutes ago may not be there yet.
AltFTool does this too
If you would rather not leave the site, Package Version Checker covers the same job here — free, no account, and it runs in your browser.
Open Package Version CheckerQuestions
Works the moment the page loads. No account, no email, no trial. Figures assume you import the whole package, and very recent versions may not be analysed yet.
Yes. Bundlephobia sends your input to its own servers to process it. That is fine for public material; for anything containing personal data, use one of the on-device tools instead.
Figures assume you import the whole package, and very recent versions may not be analysed yet.
Alternatives
Same category or same task, ordered by how closely they overlap.
caniuse.com
Answers whether a browser feature is safe to ship yet
codepen.io
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Chains encoding, hashing and decryption steps into a repeatable recipe
devdocs.io
One fast search box across a hundred API references, usable offline
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Decodes a JSON Web Token into readable header, claims and signature