- CSS Battle -- take challenge to create CSS objects.
- appium — Automation for Apps (used to testing UX on different devices, more exact than Browser Inspector).
- Facebook Sharing Debugger tool — check if your urls display correctly or not on facebook.
- Fontello — make an icon as a font (there are also Awesomefont).
- BestFonts.pro — Free fonts for WEB and Photoshop (may be illegal).
- google-webfonts-helper — A Hassle-Free Way to Self-Host Google Fonts — giving us font files and font-face declarations based on the fonts, charsets, styles, and browser support you select.
- Happy Hues — Not sure what colors to use in your designs or where to use them? Happy Hues is a color palette inspiration site that acts as a real world example as to how the colors could be used in your design projects.
- HTML characters: copy & paste HTML characters.
- JavaScript Event KeyCodes — get the keycode of any key when you press.
- Regular Expression 101 — rules and transform directly.
- RequestBin — A modern request bin to collect, inspect and debug HTTP requests and webhooks.
- Responsively -- A modified web browser that helps in responsive web development. A web developer's must have dev-tool.
- Tiny helpers — A collection of free single-purpose online tools for web developers.
- Wayback mahine — an internet archive (to check old/dead websites).
- For drawing / illustrating:
- Chart.js — Open source HTML5 Charts for your website.
- Excalidraw — Virtual whiteboard for sketching hand-drawn like diagrams.
- JSXGraph — JSXGraph is a cross-browser JavaScript library for interactive geometry, function plotting, charting, and data visualization in the web browser.
- Rough.js
- Three.js – JavaScript 3D library
- Two.js — a two-dimensional drawing api geared towards modern web browsers. It is renderer agnostic enabling the same api to draw in multiple contexts: svg, canvas, and webgl.
- Vector.js — Vector is an open source javascript library for creating interactive graphics.
- Zdog — Round, flat, designer-friendly pseudo-3D engine for canvas and SVG.
- For visualizing data:
- Matter.js — a 2D physics engine for the web.
- Stage.js — 2D JavaScript library for cross-platform HTML5 game development.
- Text & Editor:
- markdown-it — Markdown parser, done right. 100% CommonMark support, extensions, syntax plugins & high speed
- Quill — Your powerful rich text editor.