NOTE: I do not receive any benefit from the links on this page (or from you by clicking on them)
1. Squoosh - Image Compression
https://squoosh.appSquoosh helps me optimize my images with its superb compression algorithm as well as the option to resize images. It's a must have!
2. Optimizilla - Bulk Image Compression
https://imagecompressor.comAnother image optimizer but this time - in bulk. Upload up to 20 images at a time and get them back compressed. Super easy!
3. Adobe Color - Color Swatch/Palette Explorer
https://color.adobe.com/exploreThe former Adobe Kuler - the tool that helps me explore new color combinations, what's trending or, if I have a couple of colors - what can I add to those in order to make a complete color palette.
4. Colorzilla - CSS gradient generator
https://www.colorzilla.com/gradient-editorI never learned how to write CSS gradients. I've always been generating my gradients using this tool.
5. Google Fonts - Font Library and CDN
https://fonts.google.comMy favorite font library whenever I need a font.
6. check-domains - Sitemap Generator
http://www.check-domains.com/sitemap/index.phpTool for generating a sitemap for your web app.
7. Pexels - Free Stock Images
https://www.pexels.com/This is where I get my generic marketing/stock images when building a website.
8. Caniuse - HTML/CSS/JS feature browser support check tool
https://caniuse.com/Not sure if you can use some browser API? Use caniuse in order to get a good view of what's the browser support as well as some nasty bugs in different browsers.
9. Toptal - CSS Backgrounds Pattern Library
https://www.toptal.com/designers/subtlepatterns/A large collection of pattern images to use on repeat for your css backgrounds!
10. Unsplash - Free Image Gallery & Random Image Service
https://source.unsplash.com/A convenient service for some mock images while you are developing an app! Just request https://source.unsplash.com/featured/?{KEYWORD},{KEYWORD} and you get an image that matches your keywords somehow. You can even add optional size: https://source.unsplash.com/1600x900/?nature,water
11. mockaroo - Realistic Data Generator
https://mockaroo.com/Super useful service which helps you generate a large set of custom defined JSON schema items. You can add object fields to define the schema you want. There are lots of predefined data types on which you can also set restrictions etc. Totally worth it!