This document provides a list of 100 essential web development tools organized into categories such as functions and classes, CAPTCHAs, date manipulation, image manipulation, form validation, Ajax and JavaScript tools, APIs, IP locations, charts and graphs, maps, audio players, video players, video conversion, and WYSIWYG editors. It introduces each category and provides 3-4 examples of tools for each to help developers find the right third-party solutions for their needs and save time in the development process. The author is Neil Skirrow, a professional web developer and director of a UK software company.