Free online tools
Colors
Color picker, tools for modifying or generating colors
Date and Time
Measure time, calculate distance between dates, chronometers
Files
Convert, compress, join or split
Mathematics
Tools for common mathematical tasks
Numbers
Work with numbers, generate, filter, sort
Programming
Tools for programming and web development
Randomness
Generate random numbers, randomize lists, common distributions
Texts and lists
Work with lists and texts, sort, randomize, reverse