What is the difference between <script>, <script async>, and <script defer> tags?

• <script>: HTML parsing stops, the script loads and executes, then HTML parsing resumes. It blocks rendering.
• <script async>: The script loads asynchronously, parallel to HTML parsing. As soon as the script is loaded, HTML parsing is interrupted to execute the script, then resumes. The execution order of asynchronous scripts is not guaranteed.
• <script defer>: The script loads asynchronously, parallel to HTML parsing. Execution is deferred until HTML parsing and DOM construction are complete. The order of deferred scripts is preserved according to their order in the document.

Here is a table summarizing the differences:

Attribute	Loading	Execution	Blocks HTML parsing	Script order
absent	Synchronous	Immediately after loading	Yes	Guaranteed
async	Asynchronous	Immediately after loading (if HTML is still parsing)	Yes (during execution)	Not guaranteed
defer	Asynchronous	After full HTML loading and DOM construction	No (except during execution, but after HTML)	Guaranteed