Toolbox

Online tools

Developer aides

AST Explorer

Places for your code

Observable

Observable is a better way to code. Discover insights faster and communicate more effectively with interactive notebooks for data analysis, visualization, and exploration.

See this introductory series to get up to speed.

Glitch

Glitch is the friendly community where you'll build the app of your dreams.

CodePen

CodePen is a social development environment for front-end designers and developers.

jsComplete

This is the simplest way I found to write React code like you would in a notepad. You can't save your work, but it's perfect for quick sketching. It also loads the latest version of React.

JS Bin

JSFiddle

Performance, optimization

Statoscope

A detailed Webpack bundle analyzer.

SVGOMG

Online GUI for optimizing SVG files with SVGO.

Squoosh

Mapping

geojson.io

geojson.io is a quick, simple tool for creating, viewing, and sharing maps. geojson.io is named after GeoJSON, an open source data format, and it supports GeoJSON in all ways - but also accepts KML, GPX, CSV, GTFS, TopoJSON, and other formats.

Overpass Turbo

A web-based data filtering tool for OpenStreetMap. With overpass turbo you can run Overpass API queries and analyse the resulting OSM data interactively on a map. There is an integrated Wizard which makes creating queries super easy.