Below is the list of some good & free online tools that can assist you in web development in ways like validation & optimization:
Front-end tools:
- JS Beautifier – Beautify, unpack or deobfuscate JS, HTML, JSON etc and make them readable
- JSON validator – help with debugging JSON and making them readable
- HTML Formatter – formats a HTML string/file with your desired indentation level
- Image to Data URI – utility to convert an image into base 64 data URIs for embedding images
- Feed Validator – validates Atom and RSS feeds
- JS Fiddle – online tool to do front-end coding & view LIVE changes
Back-end tools:
- WSDL – Soap Client – webservice testing tool that allows you to debug WSDL files
- SiteMap Validator – provides validation of your Google Sitemap
- RegEx Fiddle – play with regular expressions
- RegEx Debugger – visual regex tester and helper
Creative development tools:
- Color Contrast Checker – indicate contrast level to satisfy WCAG AA standard
- Color Scheme Designer – helps designs color themes for website
- PreLoader Generator – create custom animated loader images
- Icon Finder – the best place to find icons of all sizes
Digital Marketing:
- GoogleBot Simulator – simulates exactly how googlebot sees your pages
- iOS Simulator – online simulator that spoofs user agents and allows you to surf the mobile internet from the comfort of your desktop browser
- Responsinator – helps website makers quickly get an indication of how their responsive site will look on the most popular devices
- SEO Center – bunch of SEO tools
- Google URL Shortner – URL shortner service from Google
Tools to enhance productivity:
- Copy Character – copy special characters that aren’t on your keyboard
- Jotti Virus/Malware scanner – scan any suspicious file or email attachment for viruses
- Google Webfonts – collection of open source fonts
- Wetransfer – sharing really big files online
- GTMetrix – help you develop a faster, more efficient, and all-around improved website experience
Please feel free to contribute more to this list….