Introduction

This is a glossary for web development.

It includes more than 3,000 (indeed, more than 3,700) terms and abbreviations.

The glossary covers the major standards and concepts of the Web, beginning with HTML, CSS, JavaScript, accessibility, security, performance, code quality and testing, internationalization, localization, frameworks and editors and tooling. It then includes other disciplines of interest and relevance to the modern developer, like computer science, design, typography, usability and user experience, information and project management and more. It goes beyond web development to feed curiosity, about the Web and the technologies and processes used to build it.

That is, this is more than a glossary for web development.

What’s more, this glossary tells a story, though it does not do so in the same way other books do. It tells a story that is sterile yet messy. It tells a story that only started three decades ago and that is still unfolding. It tells a story that starts with you. Why you? Because you are on your own web development journey—and because web development is only unfolding, only so alive, because of people like you, people who take a personal interest in it. When you read this glossary like you would read another book, you may notice. (Yet still, it is a glossary.)

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It has been neither necessary nor desirable to come up with a new and different explanation for every term. About 60% of the definitions in this glossary are based on Wikipedia, and about 5% on MDN Web Docs.

Left arrows (“←”) signify sources such as Wikipedia and MDN Web Docs, linked to the respective original material.

Right arrows (“→”) point to the expanded forms of abbreviations, and to common synonyms and expressions. Sometimes they take you on a little detour, as with Personal Home Page → PHP → Hypertext Preprocessor, or HTML 5 → HTML → HyperText Markup Language. This may seem lengthy, but it aims to make meanings, relationships, and sometimes history more clear. A right arrow may also point at a term that encompasses the referring term, or at a related concept, and therefore does not necessarily indicate identity or equivalence.

Up arrows (“↑”), followed by a URL, point to additional information, like company and project pages as well as specifications.

Some terms and abbreviations have several meanings. Only the web-related ones are shown.

Sometimes there is imprecision: Is a home page a special type of web page, but a homepage another word for a website? (For this book, which tries to gauge how most people use the respective terms, this is so.)

Unfortunately, there are going to be inconsistencies, errors, and maybe controversy. Please help improve the glossary as well as, if applicable, Wikipedia and MDN Web Docs. Giving back to both projects, work on this book has led to numerous small improvements to both Wikipedia and MDN Web Docs articles, but it is improbable that these improvements covered all there was to improve. Thank you for sharing your knowledge and taking the time to contribute as well.

That all being said: Enjoy. Web development is a great field.

—Jens Oliver Meiert

Licenses

The Web Development Glossary 3K is licensed under a CC BY–SA 4.0 (Attribution–ShareAlike 4.0 International) license.

Many explanations build on Wikipedia. They are marked “Wikipedia.” The original material is licensed under a CC BY–SA 3.0 license.

Other explanations build on MDN Web Docs. They are marked “MDN Web Docs.” The original material is licensed under a CC BY–SA 2.5 license.

A few explanations build on the HTML Living Standard. They are marked “HTML.” The original material is licensed under a CC BY 4.0 license.

All original material has been shortened and edited.