Developer tools that install from the browser

The reference that works on a plane

DevDocs is the one to install first. It pulls the documentation for most major languages and frameworks into a single search field, and caches it — so it answers instantly, and it answers with the network off.

That is a genuine change in behaviour rather than a convenience. A reference you can trust offline is a reference you stop tabbing away to a search engine for.

Tools that answer one question

regex101 explains, token by token, what a pattern actually matches — which is faster than reasoning about it. crontab.guru does the same for cron expressions, where the failure mode is a job that runs at the wrong hour for a month before anyone notices.

jwt.io decodes tokens. The reason to use the installed version is not speed: it is that a token pasted into a page you do not control is a token you have leaked.

Things that process files without uploading them

Squoosh compresses images entirely in the browser, comparing codecs side by side. Nothing is uploaded, which matters when the image is a screenshot of something internal.

SVGOMG optimises SVG the same way, and bundlejs bundles and reports the size of a package before you add it to a project.

If you are building one of these

The two failures we see most often when checking submissions are a manifest that declares itself and a service worker that caches nothing, and an install prompt that never appears. Both are common enough that we wrote them up: why a PWA is not installable, and the blank screen after install.

When it works, you can list it here — the standard listing is free.

Frequently asked